Always state your parameters when you need to know about coral behavior: this is what they ought to be:
alk: 8.3-11
cal: 400-420
salinity: 1.024-6
temp: 80.
nitrite, nitrate, ammonia all 0.
If your water varies at all from these, look there for your reason. These corals do not like ammonia at all, period, and they are very sensitive to alkalinity out of params.