Coral problem

[Kershaw]

First thing I would do. Is get some water and test it. If it's good then do a big water change and test again.

Your goal for peramiters should be
Ph-7.8-8.4
Kh 7-11
Cal around 450
Mag around 1350
Ammonia 0
Ammonia 0
Ammonia 0
Nitrite 0

 

[nervousmonkey]

+1 to what @Kershaw said. Ammonia 0, Ammonia 0, Ammonia 0
Ammonia, even small amounts, will kill corals quickly. Id' figure out why you have ammonia present... Have you treated your tank with anything that could kill bacteria, like antibiotics for any reason?