have to take them out and nurse them in yr sump or a separate tank for the time being. Dose amino acids n feed them with some chopped meaty prawn or fish, or henry's gourmet or other forms of coral foods for LPS, might help them to recover from tissue lost. u have to play doctor for a few weeks n hopefully, they will recover.
not too sure abt the acropora...hope some sps specialists here can help.
meanwhile, check yr water parameters.