Coco grow veg problem day 21

Hi everyone!

Thought maybe someone could share their wisdom, as I am out of thoughts this time. This is my fifth coco grow. There have always been some yellowing problems in past starting seedlings, but never this far into vegetative growth.

Plants: 2 x dinfem Original Amnesia fem.
Both plants 21 days from sprout (as you can see one plant is behind in growth for some reason)
Medium: 100% Canna coco Professional Plus
Feeding: Hand watering every other day with tap water PH 5.7-6.0 (water stays 1 day in room temperature and PH brought down with vinegar before feed). 10-20% run-off with PH 6.0 (Also 2 times I let them almost completely dry). Using canna coco A+B 1.2 - 1.5 ml / Liter .
As this seemed first typical cal-mag def I foliar sprayed them with epsom salt (5-6 times). Also added some epsom salt to feeding water. Stopped giving epsom salt 4 days ago, as this didnt seem to help.
Light: First used 125W CFL, but as I got my first ever HID system going, now I use 400W HPS (Superplant Agro for veg and flowering, 30% blue spectrum added). I plan to use this light to the end. Light is 18 inches=45 cm away from plant tops.
Setting: 1 x 1 x 2 meter grow tent BlackBox Silver. I have two fans blowing in tent constantly (1 straight to plants, other straight to light bulb)
Temps: 89-90F (30-32C). I know not ideal, but I have grown in past with this this temp. No big problems

As you can see from photos the older leaves are browning and die. New growth first seems green, but after 1-2 days yellowing starts again. Also the smaller plant seems more affected by it, stunted growth.

PS. I also did a full flush with PH-d water 6 days ago (I fed them too much: 2ml A+B). After flush things seemed greener for a while. But now the yellowing is back....

Thanks for your thoughts!

Any ideas?

Yes, you're over ferting.
coco is a dense material that will hold nutrients for a while. don't spray anything on them. look at the ingredients of the ferts you're using. if they have many nutrients, you shouldn't need to use anything else. don't add anything as a guess. know what mg def looks like before you try to add more. you don't have mg def. you might be able to feed less often and just give water if the coco dries out. are you sure that the amount of fert you're giving is correct for plants of that age? maybe consider dwc instead. you'll get rapid growth.

Add 0.5 gram of magnisum for each gallon of water.

Take it easy with feeding as u almost burn them.
Give 1.3 EC at this stage

I don't agree that your over ferting, maybe watering too often. I don't imagine a plant of that size would need watering every other day in pure coco.
Signs of classic mag def, yellowing between veins, vein stays green, yellowing and browning on tips which can look like nutrient burn but don't think it is, symptoms on lower growth and newer growth green, twisted growth ect.
Mag is better absorbed from 6-6.5 ph, I would ensure your giving it 6.2 which is the top end of what scale I use in coco.
However to ensure your ph is stable I would stop using vinegar and get a bottle of ph down, it will last you a long time and is more stable than vinegar. Vinegar can multiply a bit like yeast which could change ph in the medium further.
That should help the magnesium in your tap water get into your plant by the roots rather than foliar spraying.

For what its worth it helps to vary the ph when growing in coco, 5.5-6-2, this allows all nutrients to be absorbed easier. For now I would keep it on the top end of that scale. You wont fix the already damaged leaves but should stop it spreading.

When your watering has the pot dried out a lot? If you use the top few inch is dry idea it can be misleading, fans and hps lights and high temps could just be drying out the top of the medium rather than the roots drinking the nutrients thus leading you to think they need watering. Better to water less often than too often. You don't want your roots fucked because that will lead to problems through the whole grow.

anyway good luck sorting it out. Up that PH slightly and give it time.

Hey. Thanks a lot for the opinions! I was reading an article about light burn (http://www.growweedeasy.com/cannabis-light-burn) . Can it be that my 400W HPS is doing that to the girls? Because the feeding schedule should be OK, as I have used Canna A+B always in past grows. At the same I remember that slight yellowing was going on even with my CFL light (picture attached). Also today came to check the plants, and I think they are continuing the yellowing and browning (bottom leaves for now are crisp and half-dead). Photos attached also from today.
The new growth is always promising and green, but in 2 days the yellow takes over and turns them almost pale....

PS. I have read very contoversial opinions about coco watering: some say it the same as hydro - no over watering possible. And everyday feeding should be ok. Then there are others to say use it as more like soil (to let it dry etc).

Confusing as hell....I thought because of yellowing continues I would flush them today again with half-strength solution. But then again - I just watered yesterday....

Hey, you treat coco like hydro in respect of the ph but in hydro you have either waterfalls like in nft or air stones or both all hydro systems. The reason being to keep the water full of oxygen which is what keeps the roots healthy and white instead of turning brown and rotten. Rotten roots are hard to come back from. Coco, although it has excellent draining properties can be over watered and thus you end up with too little oxygen for the roots to do their job. This is why some people add perlite to coco, I helps drainage and creates more micro pockets for oxygen. Same for other things like hydroton(clay pebbles).
So overwatering is possible and since you leave your water to sit at room temp it will dissipate a lot of the oxygen in there before you use it. If your roots are not taking in the amount of water you are putting in then your adding more every other day then it can be a route to steadily turning your roots rotten. So better to water less often than to risk it.

As you say, the new growth starts off fine and then goes tits up, still think its mag def, I just hope its due to PH rather than a lock out or root problem.

Light burn, I would say it would be more at the tops and the tips which get the most light, it doesn't seem to be from the pictures.
A 400w is nothing major, I have never had light burn using 1800w of hps about the same distance away as yours. It cant hurt you to raise your light 6" though. I have to say I don't see temps in the 90degree range.

Going back to the watering, I'm not saying your defo overwatering, I just know the problems it can create when that happens and its one hell of a nightmare.

Take a look at the many charts for nutrient uptake PH in hydro online and you will see the PH is very relevant to mag uptake. As your familiar with growweedeasy in the mg def page on that site it states magnesium is best absorbed at PH6-6-5. I don't think that counts for foliar spraying obviously. But tap water unless its softened should contain plenty of mg, just give the roots the best chance of using it with a slightly higher PH.

Thanks Corey! Your explanations seem logical. I also crossed out the light burn thing as it should affect the top of plant, not below old leaves.
So this is what I did 5 minutes ago: I gave them epsom salt-watering. 1.5 ml dissolved in hot water and added it to 1L tap water PH´d to 6.3 . Both plants received 1L of such solution. No nutes added this time. I guess now I won`t be watering tomorrow or maybe even day after?

PS. I checked the run-off and it was showing 6.8 today? I think not a catastrophe?

With that run off maybe you have had some salt build up. Its a tricky thing run off though. It doesn't always tell the full story.

Give them time to dry out now and keep an eye on how they progress, don't get drawn into doing to much to them too often. We often love our plants to death. Good luck with them!

It's not too confusing if you think about what you're growing in. It can't be like hydro because such dense material as coco traps water and nutrients inside, and keeps air out. This can be a bad combo. I don't know why people keep using coco. maybe it should be mixed with perlite as mentioned. it's just too dense by itself. I suspect that this is the only real problem and playing the feed/flush game just makes things worse. also, flushing with half strength ferts isn't a true flush. I said earlier that it's over fert based on some dark green leaves with leaf tip yellowing/browning. EC numbers vary depending on which device or method you're looking at (there's more than one). One thing I do know is that people come here complaining about their coco grow not doing well.

I actually grown in coco / mixed with perlite. And I have had beautiful results. This time I just made dumb mistake and FORGOT to add perlite! I don`t know if this doesn`t go any better - how can I replant almost a month old plant ?

I even don`t go checking on them today. Just not to inerrupt with the fatherly over-caring again

BUT I thought I would cut out a fragment of the photo that I think shows the deficiency most precise

Attached below for your extra thoughts!

So, checked the situation today (after the epsom-salt watering 2 days ago / no nutes). And as you can see from photos there is actually real progress and new growth looks green. So what can be concluded? This whole mess was actually Magnesium deficiency? I really-really hope the new growth stays green and lush! I fed her 1.3 ml / 1L A+B with PH 6.0. Or should I continue adding epsom too?

As for the other / smaller plant - the progress has been minimal (still not much new growth, maybe a little more greener though). I decided to transplant her in new 30% perlite / coco mix. Hope this gets more air to her roots, as the roots were really tiny and narrow. The transplant was not easy for her: many roots did break off. I hope she recovers - let`s see how it goes....fingers crossed!

since you made two changes, water without nutrients and added mg, it's close to impossible to know what the real issue was. if you want to find an answer you should only make one change at a time. this doesn't look like what I've seen of mg def. people love to say that's the problem, but the truth is they don't really know. I stand by my idea that it was over fert because you're growing in dense coco and it looks like you were feeding too much.

Just wanted to give my thanks for your kind suggestions with an update. There they are - 11 days after last post in photos below. The bigger girl is a real mother plant as you can see. The smaller one just doesn`t want to grow that bushy and her yellowing/deficiencies took longer to cure, but I hope some smoke will come out of her too anyways. Overall I`m real happy with the situation

Anyways there they are (4 full weeks in veg, Im gonna veg them for 5-6 weeks).

SideNote said:

Hi everyone!

Thought maybe someone could share their wisdom, as I am out of thoughts this time. This is my fifth coco grow. There have always been some yellowing problems in past starting seedlings, but never this far into vegetative growth.

Plants: 2 x dinfem Original Amnesia fem.
Both plants 21 days from sprout (as you can see one plant is behind in growth for some reason)
Medium: 100% Canna coco Professional Plus
Feeding: Hand watering every other day with tap water PH 5.7-6.0 (water stays 1 day in room temperature and PH brought down with vinegar before feed). 10-20% run-off with PH 6.0 (Also 2 times I let them almost completely dry). Using canna coco A+B 1.2 - 1.5 ml / Liter .
As this seemed first typical cal-mag def I foliar sprayed them with epsom salt (5-6 times). Also added some epsom salt to feeding water. Stopped giving epsom salt 4 days ago, as this didnt seem to help.
Light: First used 125W CFL, but as I got my first ever HID system going, now I use 400W HPS (Superplant Agro for veg and flowering, 30% blue spectrum added). I plan to use this light to the end. Light is 18 inches=45 cm away from plant tops.
Setting: 1 x 1 x 2 meter grow tent BlackBox Silver. I have two fans blowing in tent constantly (1 straight to plants, other straight to light bulb)
Temps: 89-90F (30-32C). I know not ideal, but I have grown in past with this this temp. No big problems

As you can see from photos the older leaves are browning and die. New growth first seems green, but after 1-2 days yellowing starts again. Also the smaller plant seems more affected by it, stunted growth.

PS. I also did a full flush with PH-d water 6 days ago (I fed them too much: 2ml A+B). After flush things seemed greener for a while. But now the yellowing is back....

Thanks for your thoughts!

Click to expand...

The doses of Canna Coco A/B you're using are conservative such that you you should add nutrients daily. Based on my experience with the canna line, you're probably only adding about 300 - 400 ppm nutrients with those doses and to then come back later and knock away those already LOW nutrients levels with pH adjust water is leaving your plant highly deficient for being at their state.

I would boost to 2 mL/L from now on and water w/ nutrients EVERY feeding. 2 mL/L would yield about 400 - 500 ppm nutrients which is also very conservative.

Of course, with coco, you always want to let things dry out a little...go about 75% light weight before feeding with nutrients-laden water.