Has anyone ever had their MH lights burn corals? i seem to have a few acros and montis losing colour and having tissue loss where one particular light shines on them. it only happens where the light hits them, not on the undersides. not all corals under the lights seem to get "burned" though... my water water params are all good. almost no phos, no nitrate, ca 450 kh 8 etc. only thing wrong in the last little while was my temperature being around 20-21, as my digi thermometer was reading about 3 degrees too warm.
its not a new bulb, its a 150w de Arcadia 10k. it is in the same fitting with the same UV glass as my other two which don't seem to do the same thing.
any ideas?
scuse the bad pic, but you can see that the coral on the left is brown on one side, blue around the middle and dead on the side that the light was shining on