Striped leaves - Why does this always happen to my young plants? I can’t figure it out!

Sick Plants & Problems
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This is my ~4th grow attempt and I’ve searched far a wide for an answer to why my seedlings always develop dark/light stripes on their leaves. This usually goes away as they move into the flowering phase.

I’m using a 50/50 mix of coco:perlite, House & Garden nutrients, currently at an EC of 1.4 and a pH between 5.8 and 6.1. The ladies are 18 days old since popping out of the medium. They’re autoflowers from Mephisto Genetics, and I’m giving them 12,000 lux (no PAR meter) on a 24/0 light cycle.

As you can see in the photos, one plant (the middle one) looks worse than the others: the growth is lighter green and the stripes on the leaves are more pronounced, but the other two also show the stripes a bit.

I thought maybe it could be something with calcium or magnesium but I’m following H&G’s nutrient schedule exactly, and foliar feeding with cal-mag hasn’t helped in the past. I also TRIPLE buffered the coco in cal-mag solution this time, then flushed it until I saw the runoff hit 0.4 EC.

What do you guys think could be the cause? I’ve asked everyone I know and posted on other forums but I still haven’t solved the issue. I’d GREATLY appreciate any advice!

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Best I can offer.

Quick Guide - Lux Levels for Optimal Cannabis Growth

Life Stage Maximum - Good - Minimum
Vegetative 70,000 lux 40,000 lux 15,000 lux
Flowering 85,000 lux 60,000 lux 35,000 lux

< 15,000 lux - sparse or “stretchy” growth - plant isn’t getting enough light

15,000 - 50,000 lux - good amount of light for healthy vegetative growth

45,000 - 65,000 lux - optimal amount of light for cannabis plants in the flowering (budding) stage

70,000 - 85,000 lux - a lot of light, some strains do okay at this light level, but some plants lose their top leaves early under this light intensity, especially plants that are not resistant to heat/light (like many indicas)

85,000 lux - at this light intensity, you’ve hit the plant’s “saturation point” which means your plant can’t use all the light (be careful of light bleaching!)

I’d say lower the lights a little more. Ideally 15" to 24" away from plants, What setting is your light at?

Also, they are Autos, you don’t need 24hr light cycle, plants also grow in the dark. I’d go with 20 on & 4 off if your looking to max output.

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The H&G line is buffered as fck. Also almost half of the EC comprises ballasts (even more for the aqua flakes).
I guess you’re not deciding to lower it at 5.8 (almost a rockwhool PH) but your water or another nutes/bonus that make it drift. Searching the factor of acidification should be your priority.

The Magic Green in foliar do miracles with nutes unbalances and PH burns, you just have to let dry a bit the medium during the process (no watering).

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Autos do get hungrier quicker as well…looks to me like either they went through a ph swing in the media or are underfed k-p

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Try 50ppm Epsom with every feed , up it to 100ppm if after a couple of weeks new growth ( not old ) still affected

Looks like mag def

Wouldn’t be enough mag in a calmag folier to fix that

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Yeah + :100: ifish! Was gonna say the same thing ^^

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If you see burnt tips from the higher ppm/ec in total feed with the added Epsom, then dial down the base feed ppm/ec to accommodate the ppm of the added Epsom
: )

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You guys are amazing! I really appreciate all the advice.

Regarding the lights, I thought the recommendation of 15,000 lux - 40,000 lux is for an 18/6 light cycle. In the past, I noticed light burn above 25,000 lux during flowering since I’ve kept it at 24/0 throughout the grow. I’ll double-check this to make sure I’m not depriving them of light.

What does “ballast” mean in this context? Google is not helping me…

Are you saying you think the 5.8 pH is too low? I’ve been hand watering so far and I check the pH immediately before feeding, so would drift really be an issue here?

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It’s a mag def
: )

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Ballast salts sorry
Quick overview

Hell yeah, you’re close to the 5.5 of hydro/rockwool. It’s way too acid for coco even mixed, let it “drift up” if you can. Or investigate this acidity if it’s a passive dynamic. For PH freaks, coco have its sweet spot at 6.0-6.5. It have to be understood as the margin of the drift, if you don’t hit “the borders” : no regulation. Don’t forget that 0.5 PH is 500% more acid or more basic.

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