I bought an open brain coral 3 1/2 months ago and was doing great. Would be real puffy doring the day and looked super healthy. Last 3 days/nights it has not opened up. I haven't changed anything at all with the tank or added anything new. I have been using Phyto Feast for feeding. I've checked my water levels and they have stayed the same. I also have Xenia's, and a frogspawn, clown, lemonpeel angel, and a damsel and these are just fine. For supplements I have always used purple-up since the begining (set-up). Any ideas?