Seedlings bleaching

Hello. Recenlty I set up a small RDWC system with some autos, and this keeps happening.

I'm running plain water, no nutes, pH and ppm seem acceptable, it's spring over here so temps should be OK too. Maybe light excess? It's a 4x4 foot tent with two 300w COB panels, pink light. Ventilation is also fine, good intraction/extraction.

My best bet is light bleaching but I don't know, panels were like 40cm from seedlings.

I also use a heavy duty aquarium aireator (almost overkill but that's not an issue) and keep water level about 3cm below pot bottom. I add hydrogen peroxide and an algae killer to the solution too.

They look hungry to me. I’m not a cob grower but it doesn’t look like light burn.

Why aren't you feeding them? One looks a bit diseased with the discoloration on the cotyledon. You using coco, from the looks of it, but coco has no nutrition, it's inert(mostly) while some may be bleaching, it is a little early till be hitting them that hard, but I'd think they're starving.

Edit: the algae killer and peroxide are a bit redundant I would think. Do you have an algae problem? If not I'd cut it. Is whatever you're using specific on ONLY killing algae or is it an aquatic vegetation killer?

Johiem said:

Why aren't you feeding them? One looks a bit diseased with the discoloration on the cotyledon. You using coco, from the looks of it, but coco has no nutrition, it's inert(mostly) while some may be bleaching, it is a little early till be hitting them that hard, but I'd think they're starving.

Edit: the algae killer and peroxide are a bit redundant I would think. Do you have an algae problem? If not I'd cut it. Is whatever you're using specific on ONLY killing algae or is it an aquatic vegetation killer?

Click to expand...

I don't ussually use nutes in the first two weeks and never had a problem. The algae killer is specific for that (it's made for hydroponic cannabis), a friend uses it and never had issues. I use 250vol (65% aprox. concentration) peroxide at 1ml per quart per week, again, not much. I did have an algae infection in the first run with this system due to light leaks (killed like 16 poor seddlings ) but sanitized the system and never had it again. This time I checked the roots and the coco and saw no algae, smells alright too. I will cut on the algae killer and add some nutes and tell you if it worked. Thanks.

Just noticed your ph pen says, 7.6! That it's WAY off. Even for soil that's a bit out there. I keep mine around 6.0, a range of 5.5-6.5 is ideal in hydroponics, 5.8-6.8 in soil. If your pen is accurate, that may be more of the issue.

you're running coco in an rdwc system?