Lower yellowing leaves

Hi guys,

Long time lurker, first time poster! This is my first grow and everything I know has been pulled from this site (with a couple of other sources), so thank you for all the help so far!

First of all, here are some key details:

Strain: AUTOFLOWER - FastBuds - Cream Cookies
Age: 43 days since sprout (week 3 of flower)
Growing Medium: BioBizz Light Mix, with 30% added perlite (drainage is excellent).
Lights: MarsHydro TS1000 at between 14" and 20" (adjust every so often as she is growing a lot vertically atm, but aim for this range). The light is on 75% power.

PH going in is 6.5, PH coming out is 6.4.
PPM going in is 500, PPM coming out is 550 - Not using synthetics though, so this could be irrelevant.

In terms of nutrients, here's the deal: I only started feeding her after I noticed the yellowing. She has shown no signs of wanting any until this point (believe it or not). She has had three feedings this week with the below doseage. No sign of it being too much, but the issue has not resolved. She's in an 8L pot, so she gets 1 litre of water each feeding.

BioBizz Grow: 1.5ml per litre (currently feeding at half strength doseage).
BioBizz Bloom: 1ml per litre (currently feeding at half strength doseage).
BioBizz Alg-A-Mic: 1ml per litre (no NPK)
BioBizz CalMag: 0.2ml per litre <---- I think this might need upping to fix my issue.


I'm at a bit of a loss with this one. The issue started around 7 days ago, with some slight yellowing of the very bottom leaves. Here's the progression:









I've had to remove the above leaves as they were 100% yellow. The issue has now moved onto the set above, and here's how she looks today.







She's drooping because the lights just came on, but as you can see, all of the other growth looks tip top:



My gut is telling me it's a mag deficiency.

Any help for this nooby would be greatly appreciated! Cheers guys!

Dont sweat that stuff when rest of plant is healthy and lush...just rip those leaves off and forget about it.

mudballs said:

Dont sweat that stuff when rest of plant is healthy and lush...just rip those leaves off and forget about it.

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The issue is that if I rip them off, it'll progress further up the plant to the next ones - she's 'stealing' nutrients from the lower leaves first. If I was nearing the end of flower I'd be leaving it for sure, as I know it's natural at that point, but 3 weeks into flower I think it's best to fix it.

I don't think it's an N deficiency because she doesn't need much N at this stage, and given the last three feedings with PH and PPM in check with no improvement, I'm guessing it's not a P or a K deficiency either.

I love learning about these plants as much as I do growing them, so would be good to understand why it's happening, even if the course of action was to rip them clean off.

I’m no expert, so please don’t just go by me, but I think they’re hungry. I think your ppm should be about double right now (1000-1200), and I would also think they need more than 1l of water if in a 8l pot. I’ve always heard you want to water around 20-25% of your container size, I could be wrong though. I’m using 10gal fabric pots and I give 2gal per feeding. Not sure if this advice is accurate, but it’s what came to mind

The lower leaves yellowing is N deficiency,Your on the right track,just up the N part or calmag as it also has N.
Plants in flower still need N.

I would up the nutes a little bit. She's feeding on herself..

add a 1/2 tsp of regular unscented Epsom. Calmag is mostly Cal, the Epsom helps a lot.

mudballs said:

Dont sweat that stuff when rest of plant is healthy and lush...just rip those leaves off and forget about it.

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I agree. I probably wouldve removed those leaves anyway to increase the airflow but this is typical of an aging plant. Its a good thing at this stage because you want to really use the available nutes up -less to flush out before chopping.

.2ml of calmag is nothing. Bump it up to 3-5ml per gal.

Jesus tap dancing christ its an autoflower! In mid flower! You aint stopping or fixing anything...if you look at the pics he's redlining that plant on nutes, look at the tips...look at the dark dense green. Just rip those few dying leaves off and be happy you got a successful grow.

You might have ran out of root space. If so, than you three biggest fan leaves in the midlle of the plant will suit the same tuxedo soon…

mudballs said:

Jesus tap dancing christ its an autoflower! In mid flower! You aint stopping or fixing anything...if you look at the pics he's redlining that plant on nutes, look at the tips...look at the dark dense green. Just rip those few dying leaves off and be happy you got a successful grow.

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It being an autoflower has no bearing on nutrient deficiency, that's just plant biology - there's nothing special about autoflowers in that regard... perhaps the fact they need less than photoperiod, but that's where it stops. If I stunted the plant then sure, that'd be a big mistake for an autoflower and would significantly affect yield, but she isn't stunted - she's putting on 1inch vertical growth a day at the moment, and this issue can 100% be fixed, it's just finding the deficit - whether it's Mg, N, P, K, or something else entirely.

The burnt tips were from week 2, when I fed without the soil being depleted. Burnt tips can also be a sign of K and Mg deficiency, and are often mistaken for nute burn. This plant is on her 6th week, and in total, has had about 4ml of grow nutes, and 3ml of bloom - that is nothing for 6 weeks growth.

I really do appreciate the replies, and I get that I could rip the leaves off and still profit from a successful grow, but I want to understand why this happens because it genuinely interests me. I care as much about yield as I do about the biology and journey of the plant.

Thanks for the replies guys, it really is appreciated. I'm taking that I'm underfeeding her, and I'm going to up the Mg next feed to a bigger dosage, alongside a full strength feed given the low PPM.

Hazey_Dazey said:

It being an autoflower has no bearing on nutrient deficiency, that's just plant biology

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plant biology? so do you know about the life cycle of the plant you're growing? just say no and save face ok.....so this is end of life for an autoflower. It matures, ripens, there is no seeds so the annual dioecious plant begins senescence....you know what....why do i even try, honestly..
you are 100% right, it can 100% be fixed.....you have fun with that champ.

mudballs said:

plant biology? so do you know about the life cycle of the plant you're growing? just say no and save face ok.....so this is end of life for an autoflower. It matures, ripens, there is no seeds so the annual dioecious plant begins senescence....you know what....why do i even try, honestly..
you are 100% right, it can 100% be fixed.....you have fun with that champ.

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You're right, why do you try? You come across as a bit of a dick if I'm honest, and to new members of the community? Nice touch. And please, don't patronise, it's not difficult to understand the basics. Don't confuse post-count with knowledge. I know I am underfeeding my plant, I am asking for more experienced growers of marijuana, in their experience, what this deficiency is, before I commit to anything. I could make a pretty good educated guess, like I did in my original post, based on my experience of growing other crops, but I want to be part of the community and thought this was something I could get help with in order to solidify my thoughts before committing to anything.

If you think this plant no longer has the ability to divide cells and grow, I don't want to take your advice anyway; I've just told you it's packing on 1 inch vertical growth a day, which is a common trait of early flower, but I guess if you didn't ignore that fact you wouldn't have been able to use the word senescence. Natural fade occurs toward the end of flower, which is when you really start to visually see cellular senescence take effect. This plant is barely two weeks into flower with 100% white, not orange, pistols, it is categorically not natural fade, and everyone, other than you, knows that for some reason; judging by your flippant remarks, I suspect you're like this quite often around these parts; it's not a good look.

Once the issue is fixed, I will gladly post an update here to back what I've been suspecting up. In the meantime, you do you mate. Perhaps see if there's any other 'noob' posts you can assert your wealth of incorrect knowledge on.

Cannabis during the stretch consume a lot of food. It’s not out of the normal for a plant to show a deficiency in this stage. Simple answer is next time feed the plant more when flower starts. Now this is an auto so maybe it’s a little different but cannabis needs N all the way through till the end. Good luck. I think the plant looks good compared to some you see on here.

myke said:

Cannabis during the stretch consume a lot of food. It’s not out of the normal for a plant to show a deficiency in this stage. Simple answer is next time feed the plant more when flower starts. Now this is an auto so maybe it’s a little different but cannabis needs N all the way through till the end. Good luck. I think the plant looks good compared to some you see on here.

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Thank you for the pointers, Myke. I don't get why some members struggle so much to believe it's a nutrient deficiency this early into flower.

I'm about to feed her, will be upping the strength from half to full (roughly 1000ppm) and increasing the amount of CalMag in the solution - no Epsom salts on hand unfortunately!

Hazey_Dazey said:

Thank you for the pointers, Myke. I don't get why some members struggle so much to believe it's a nutrient deficiency this early into flower.

I'm about to feed her, will be upping the strength from half to full (roughly 1000ppm) and increasing the amount of CalMag in the solution - no Epsom salts on hand unfortunately!

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Well a 1000ppm is kinda high. What did you give before ?

myke said:

Well a 1000ppm is kinda high. What did you give before ?

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Was at half strength, 500ppm, using 500 scale/TDS. There's a lot of additives in there which have trace amounts of NPK. Not sure on the PPM before the additives/CalMag, but will definitely check beforehand and calculate the PPM based on the difference.

It's worth noting that I am not using synthetic nutrients, and I am using organic instead.

Fed with full strength nutes:

3ml Bio-Bizz Grow
2ml Bio-Bizz Bloom
1ml Bio-Bizz TopMax
2ml Bio-Bizz Alg-A-Mic
1ml Bio-Bizz CalMag

1 litre of water.

Thanks for the pointers everyone. Will report back in a couple of days.