How long has the tank been set up? What kind of flow and lighting? How long has the Hammer been in the tank? Where does the Hammer sit in the tank? Any neighboring coral? These questions will all help answer.....Hammers are pretty undemanding in my experience. The only issues I have had in the past were from too strong of lights or flow. Could either of these be an issue? Do you see any type of infection on the coral itself?