I know my spectrum and par are perfect. I use a combination of Blue+, Coral+, and True Actinic (T5 lighting). Par is 350-430.Sometimes acros turn brown from too low nutrients or not the right light spectrum, I think, not sure lol. Your temp might also be playing a factor like said above you are in 26.7.
Low nutrients causes browning? Apparently browning is excess zooxanthella. My nutrients weren’t too low (my Hannah HR nitrate kit is +/- 2ppm, and I feed well (ammonia is what corals care about). I know my nitrates weren’t too low despite the hobby grade kit saying it was.
The nitrates are always show higher with the Red Sea Nitrate kit (more accurate at lower levels).
I have a mixture of browns, but come to think of it, I think pale-brown is what I’m really dealing with. They basically look gray.
Not all acros look pale/brown; some look good, such as my Walt Disney, montipora, and green slimers…the easy corals. *face palm*
Ps, I’m not rejecting suggestions. I already raised my nutrients to try to limit all the variables. I know people say low nutrients cause bad colors.