My res temp is 68 I'm using sensi A & B. have this same problem with my other rez in the next room. It started their from the beginning. And now is starting in the next room from the beginning. I think it came from some bad clones I got. They had root mites. I killed all the mites with merit 2f. The new Bach was just fine. That's why I think it is some kind of fungus that spread from the other room. I add my a&b then ph because after adding A&B it is just about 5.8 no adjustment need. I'm using RO water.