I've had a big problem with maintaining my PH once the summer started and the windows closed up for the AC to run. I finally ran the skimmer line outside and now my PH improved and coral did improve. I just came back from a 4 day trip to see almost all my sps except my 3 stylo's bleaching from the tips, sides and bases. I pulled up my apex and the temp seemed to have swung a degree or two within 24 hours. Would this be the cause. I tested all my params: SG 1.026, Alk 10, Cal 410, Mag 1400, Nitrates 0, Phos 0.04ppm. Since the upgrade to this 90, it's been nothing but headache. Here's a couple screenshots of temp and PH from the apex.