Water parameters areDefinitely a euphyllia. It would help to post a thorough reading of parameter. If parameters are in the green zone, it might be a flow or lighting issue. Also check around the coral skeleton for any type of infection or parasite. Receding flesh around the base of the coral is not a good sign. Flip the coral & give it a good inspection & if all checks out it just might need a bit more flow & light but parameters need to be shared in order to narrow down the problem, NO3, PO4, ALK, Temps, Ca, Mg, PH, etc. good luck.