Hello and welcome!
What kind of lights do you have? Even though it's a low light coral, it still needs more light than a regular tank can provide. Also, what are your water quality parameters (pH, temp, salinity, ammonia, nitrites and nitrates)? What other animals do you have in the tank, and how long has the tank been set up? Do you use tap water? Answering those basic questions will help us out a lot.
They are really easy corals to keep (probably among the easiest out of all of them), so we'll try our best to figure out what's going on. Also, can you post pics?