First grow, in coco - was going fine, until it wasn’t.

Well, it’s my first grow, and I have 2 of 3 plants showing what looks to me to be a potassium issue. However despite having been a member here for 12 years (holy shit) this is my first post and and grow. Pics, and then grow info below:

How it began, small spots on old growth



The worst of it, on the biggest plant.


The autoflower

I notice reddish stems? On affected fan leaves


Details:
2x bag seed photoperiod, 6 weeks into veg and about to be up-potted to 5gal and put to flower
1x white widow autoflower, 2.5 weeks from seed

All in 3 gallon pots with 70% coco coir 30% hydroton. Coir was rinsed to tap EC and then buffered with a calmag solution twice, and rinsed again. Fertigated by hand 2x daily to 30% or more runoff.

All plants getting 2ml/gal (half strength) GH CALiMAGic and FloraNova Grow. Bigger girls to 1.7 EC (0.3 water, 0.2 Cal/Mag, 1.2 FN Grow). Smaller girl is same, diluted to quarter and as a week ago half strength.

I usually pH to 5.6-5.7. I am wondering if I should sweep up. EC and pH are being read with a Bluelabs combo meter.

This showed up on both girls as of about a week ago, starting on the lowest true (three finger) leaves. Now has spread a bit Upward. I have dropped EC gradually to 1.4 but sure would like some eyes on this and help. What should my next steps be?

Not the problem but ph mine at 5.9 - 6.0 in coco perlite 50-50 mix.
That does look like nure burn to me...

Inthelantana said:

Not the problem but ph mine at 5.9 - 6.0 in coco perlite 50-50 mix.
That does look like nure burn to me...

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Thank ya — I need to start aiming toward 5.9. I did a heavy flush with quarter-EC 6.0 pH and today nothing looks worse. It was progressing quickly. I think you may be right.

up your ph to 6-6.1 hugging the lower limit for coco gives you a bad chance of no mag uptake.. not sayign that's your problem but since i moved my ph up a little things went much better..
Cal and mag uptake both drop off bad below 6ish..

I’m not sure it’s nute burn bc it started gradually from lower leaves up. My guess is you’re over feeding which caused a ph swing in the medium.
If you’re using Tap Water then drop the Cali magic.
Feed light and stay consistent. Feed daily at about 550 ppm. Don’t let coco get more than 50% dry.
I suggest ph the nutes to 5.9 or so if things are going well. If you like, you can do a slurry test to see where ur medium is at, then ph your nutes accordingly until the problem has been corrected.
I’ve had the same exact problem your having now.
Rinsing your coco before use with a mild nute mix may help for next grow. I never run just water through my coco. I always go straight to buffer.
If you’re using tap to feed it should be aged

best of luck

Your girl looks a little short on Mg, which as was pointed out by @icetech , most likely attributed to your slightly lower pH. I'd get closer to 5.8 or better...it's most likely all you're missing. Good luck.

What they said.

My plants in coco do better when fed @ ph 6.1 average. 5.9 thru 6.3. Ec of around 1.6.
My method...Feed lighter but more often with less runoff. Prevents salt buildup issues.


I would continue the calimagic.
Big EC swings can cause burnt tip/edges.

Going deeper into coco techno...

Yeah, it's weird how people try to ride the lowest PH possible, i used to do that also.. now if i'm between 6 and 6.5 in my dwc and coco (i run both) i have way less issues..

Nice one guys!! I've been guilty of keeping pH to exactly 5.5 constantly and getting similer issues. Do you guys this it's fine to just add ph up to a res even if you've added down? Or would you just lob it and start a fresh? Additionally is it worth foliar feeding And is this advisable in flower?

posting to come back and re-read

Lpt said:

Nice one guys!! I've been guilty of keeping pH to exactly 5.5 constantly and getting similer issues. Do you guys this it's fine to just add ph up to a res even if you've added down? Or would you just lob it and start a fresh? Additionally is it worth foliar feeding And is this advisable in flower?

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You can use ph up, that's what it's made for.. but WARNING!!! PH UP will raise the ph WAY WAY more than ph down lowers it.. the shit is crazy powerful compared to down.. so add slowly and measure..

I've been setting pH to 6.0 for years with coco. Healthy plants from start to finish. No issues at all.

xtsho said:

I've been setting pH to 6.0 for years with coco. Healthy plants from start to finish. No issues at all.

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Yeah, the difference from like 5.6-5.7 and 6.0-6.1 was amazing for me.. so many problems went away.

TintEastwood said:

What they said.

My plants in coco do better when fed @ ph 6.1 average. 5.9 thru 6.3. Ec of around 1.6.
My method...Feed lighter but more often with less runoff. Prevents salt buildup issues.


I would continue the calimagic.
Big EC swings can cause burnt tip/edges.

Going deeper into coco techno...

Understanding Osmosis and EC - Coco For Cannabis - Science

Learn how EC, PPM & TDS affect plants. Understand osmosis (how the plant absorbs water) and why it is critical to measure EC/PPM when you fertigate.

www.cocoforcannabis.com

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This is some great info you shared. Thank you.
for those of you using coco, have a read.
I recommend reading this article immediately after for a fuller understanding https://www.cocoforcannabis.com/managerunoffec/

icetech said:

You can use ph up, that's what it's made for.. but WARNING!!! PH UP will raise the ph WAY WAY more than ph down lowers it.. the shit is crazy powerful compared to down.. so add slowly and measure..

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Fucking hell nice one I would insta fuck a hole res unless u said that

Lpt said:

Fucking hell nice one I would insta fuck a hole res unless u said that

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haha yeah, luckily i use just 5gal buckets and it still pisses me off when UP makes it go from 5.5ish to 8 with a tiny bit.. just wtf lesson learned.

I also ph coco at 6...5.9-6.1 I call close enough

icetech said:

haha yeah, luckily i use just 5gal buckets and it still pisses me off when UP makes it go from 5.5ish to 8 with a tiny bit.. just wtf lesson learned.

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Have you ever used baking soda to bring ph up?

Lpt said:

Have you ever used baking soda to bring ph up?

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No.. in the last year and a half i have only had to go up like 3 times.. usually i end up around 6.6 after mixing..

icetech said:

You can use ph up, that's what it's made for.. but WARNING!!! PH UP will raise the ph WAY WAY more than ph down lowers it.. the shit is crazy powerful compared to down.. so add slowly and measure..

Click to expand...

Learned that lesson today