What's the issue! Help needed ASAP

I made the mistake of adding a small amount of h2o2 to my res and it ended up stressing my plants pretty bad. They haven't recovered really yet and it's been 24 hours. The h2o2 caused my plants to droop and curl up and get real crispy.

I added the H2o2 because I thought it would help me get rid of my real problem. My real problem is the deficiency that seems to be taking over my babies. It all started on one of them but it now seems to be happening to all of them. Can someone identify it and tell me how to treat it? I am posting pictures of my worst plant. I would really like them to recover.

They are Northern lights Autos
24 hour light cycle with 2x 6500k and 1x 2700k
In a grow box, temps around 80 degrees
Ph 5.8 or so
The res was clear and I got bad algae, that's why I added the H2o2, I thought the algae was causing the deficiency.

The deficiency that i'm talking about is the brown spots that continue to consume the leaves until they are entirely covered.

If you need more info lmk!

Thanks!

Autos are really unforgiving Id just chop em

Root rot man. You gotta read up on beneficial bacteria. Make the tea!

Completely trash them all?

What If I trim the leaves?

Edit: The roots don't look that bad, they were covered in algae but now the algae is clearing

My other plants are just starting to get it! I really need to prevent this from getting worse! Please help