dwc seedlinds droopy

hey, i have some plants going in my first dwc setup.
at the moment each bucket isint connected. working on that for my next grow was just trying to get some experience before then.

im using white 4gal square food grade pails with 6" net pots. everything was going well, three of the six clearly grew a bit faster and the roots spread out better and were coming out of the entire net pot and started down into the water. they were growing smoothly for about a week, and then all of a sudden the first one started to get droopy leaves. and then the next two followed.
Ive tried everything i can thin of from changing the water, moving the lights up, opening closing the tent to allow more air to get in, moving them from under the lights, raising humidity and just cant seem to figure out whats wrong with them. i was adding h2o2 with my water originally but Ive stopped because i thought that could be the culprit, and just have no idea whats going on.
but you can clearly see the difference between the ones that are drooping and the ones that aren't.
you should be able to click the pics to see a more zoomed in version on ibb

heres some pics with lights off and roots aswell..

thanks if anyone has any ideas!

One of the first signs of root rot is droopy leaves so I'd be looking hard at the droopy plant's roots. I used to use 35% food grade peroxide regularly in DWC to prevent rot then made a chiller and didn't need to any more. What strength of peroxide were you using and how much per liter/gal?

Are the plants all the same strain as some strains droop normally.

Air stone in each pail I assume.

As long as your water temperature is on point, maybe they just need to be top-fed lightly until they have a strong root structure? Or water level needs to be adjusted in the buckets?

I do not see any visible root issues in those pictures. Old Med is on point though, root rot and slime can cause droop!

i was using 29% h202 from my hydro store, and i was adding about 1-2ml
and yeah ive got a 70l/min pump running the 6 buckets and a 4" airstone in each.
theyre all the same strain yes, except for one. 2/5 of the one strain are droopy and 1/1 of the other are. and its all 3 that grew faster, the others didnt fan their roots out, so i had to to feed them by hand for a bit and they took longer. but i havent seen any of them droop like this yet.
water temp is one thing i havent been able to control yet, though it hovers around 19-22C. Ive got an old water dispenser that im going to retro-fit into a chiller once i get my recirculating system setup( which might actualy be this week, so i may scrap these guys anyways.)

and i had algae/slime issues at first cause i hadnt light proofed the buckets yet ( i have black round 5gal ones im using for my rdwc system, dont worry ) but that went away as soon as i light proofed them and did a full water change.

here are a couple pics of a root that i could see smoe yellow on under a microscope.
Is this root rot starting?

Yellow/brown root tips indicate that root rot has just begun...when you see the tip of the root begin to grow white again is when you've fixed the problem and healthy root growth has begun to happen again. That browning won't go away, but the newest growth won't be brown or yellow anymore. Personally I had a tough time making sterile work. If you do as well, then give Great White, Orca, or one of the other array of beneficial microbe products a try. Maybe it'll work for you, or maybe you'll prefer sterile, whatever works for you.

Time for some pool shock.