I am having issues mostly with SPS coral in my tank turning white. I keep DKH around 8.5-9.0, Calcium 400-420 and Mag around 1300. I have mixed corals in a 220 Gallon tank. It has been a ongoing issue for me. The corals will turn white, and then color back up over time. I run a Kalk stirrer and hand dose Seachem dry advantage and Calcium when needed. I would like some input on this issue. Here is a pic of a mystic montipora with spots on it, acros are effective too.