Have you tested your water for calcium, magnesium and alkalinity? That's the first step. For stoney corals, they all need to be in check.
It won't like fast flow, so make sure it's not getting battered.
Lighting - they're not too demanding.
Feeding - target feed it once in a while, but if your cleaner shrimps are ripping food from its mouth, maybe target feed them first, the the coral.