DWC 3 weeks in seedling, advice needed

Hello guys,

I'm relatively new here. i had 4 successful grows over the past 3 years. had pulled 350 grams dry from 400w hps.
Now in DWC that has been a completely different story...
After failing 5 times battling reservoir temps and root rot caused by it, i finally found to manage those problems.
Tried all sorts of sanitizers, wich managed cyanobacteria bloom but didn't sort a different kind of rotting bacteria.
Eventually, compost tea bennies seemed to resolve my problems, allthough resulting in a weekly cleaning due to 'after slime gunk'

Now from 1 problem we seem te go to another ( nute wise i guess )

Seed had been germinating fine, it was growing pretty slow but i know that is normal in dwc.
After appearance of the first true leaf, i found the seedling being a bit light in colour, so i added some extra calmag at 0.4 ec wich is 1-0-0 so besides micros contains 1% nitrogen.
I allways did this in coco with all my seedlings and never gave a single problem.

This time is different, the older leaf edges began to brown, curled upwards and started to creep more to the inside of the leaf. At first i tought that it was a light problem, but i dimmed my lighting wich lowered my temps from 25°c to 23.5°c. i then tought it was underfed due to still being light in colour. i mixed some quarter strength AN GMB and poured some over the netpot, yet the problem was still advancing. i then tought that it is burned wich i still believe till date, allthough i'm not very sure. i dumped the reservoir, flushed the netpot with clear RO water and it still got a bit worse since yesterday.

I'm really in for advice since i really don't want to loose this one either. not much time left.
Thanks in advance.

Overfeeding. That's definitely nute burn. Don't worry about leaf darkness unless they are showing problems. If they are healthy but light, leave them be. If they start showing yellow or getting dead spots, there's your sign. You're in DWC, shit happens fast, good or bad.

Any burn on the cotyledons?

Nope, healthy dark green. thanks for confirming my toughts... now 1 day after flushing /changing reservoir with pure RO, and still burning. Hope i'll still be able to pull her through...

Do you have roots coming out of the net pot?
Ive had that look when ph was too low.

myke said:

Do you have roots coming out of the net pot?
Ive had that look when ph was too low.

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Ph could be out? Hence not darkening with the increase in ec. And looks like nute burn to me. Are your lights too close?

Hydro4life said:

Ph could be out? Hence not darkening with the increase in ec. And looks like nute burn to me. Are your lights too close?

Click to expand...

Sorry missed the part where you said you dimmed your lights....

no roots yet, and i'm using AN GMB ph perfect for the first time. And from what i learned from the past,
ph isn't important as long as you don't feed.

I'm just not exactly sure how well the calmag xtra supplement is chelated. My RO water sits at 6.2ph.

Yesterday the problem still advanced from the 6th nerve till 5th. Now it seems to stay there 8 hours later.

Make sure PH is in line and drop your feeding a bit. At 3 weeks, I doubt you really need cal/mag. Most plants I've seen don't really even need cal/mag supplements until flower. My past grow I started my seedlings out of the gate at a ppm of 150, and I seriously stunted their growth by doing so, which caused their growth to delay and resulted in them taking longer to get big enough to tolerate normal doses of nutes.

Thx for the advice, the seedling was sitting at close to 0 ppm. without feeding ph never seemed to matter to me.
Now in dwc, they seem te require slightly different fundamentals. Allthough i don't believe they require ph corrections without being ferted. here are some of my results from growing coco

Just like coco dwc plants need the calmag and food.Your RO water has nothing,so it needs some food anyway.You said the seedling was at near 0???

Yes sir, they allways did in the beginning. i only started feeding at the first tri-leaf appearence. Some strains would throw rust spots so i would start low strength calmag, others won't.
i found the colour of my seedling being a bit too light, so i started my calmag supp wich is 1-0-0. That's where trouble started slightly. my first diagnose was underfeed since i never had a plant burning at that stage from calmag supplement ever before. so i started quarter dose nutrients and that fueled the problem, lost about 1/3th leaf and she kept burning now 2 days after flushing and clearing res

Hows your tap water?Maybe the seedlings will like it?

I allways used to grow in tap water in the past. it sits at ph 7.8 and has an EC value of 0.6. pretty hard and loads of alkalinity. Now with the PH perfect story i have no other choice then using RO water. now 3 days later it seems that she's still burning a bit, allthough i dumped my reservoir and replaced with RO only. never tought that it could continue for so long after swapping res. she has grown a tiny bit. still no roots showing. i can see 1 root wich poked through on the side of the rockwool wich is pure white in colour. i hope she'll pull through :/