2nd grow DWC D2W what causes this problem?

[YBGTA]

The first time I tried this and it happend, it looks like pythium or root rot but not sure, I have 3% h202 if needed but idk how much to exactly add, I also have added UC roots at 3ml/gal (the buckets holding 3gal). They have weird spotting a discoloration going on, would love to kn9w how to correct this, if I missed anything lmk thanks!

 

[Monkeybigbuds]

What’s your stats room temp room humidity water temp ?

 

[YBGTA]

What’s your stats room temp room humidity water temp ?

Mid 70s to low 70s most of the time, RH is around mid 40s to mid 50s, the tent was lower temp for awhile but around 67-68 and once I turned down my ac they seemed to be doing a little better, I guess the res was too cold? I hear ppl say 65-67f too cold for potassium uptake but I'm still very new to this, it also might be ph problems such as my pen becoming uncalibrated so, I'll be getting a ac infinity one in a few days