I have a nice sized Christmas Favia that has been doing fine for a couple months and suddenly it's started to cover itself in slime every night. Yesterday I noticed the skin decaying. All my perimeters are good. Not sure what's up. Any help would be appreciated. I have a few other SPS in the tank doing well. But 3 favias that just don't ever look happy. War coral, maze brain, and xmas just haven't looked happy lately. I would love to include photos but not sure how to.