Ensure its getting adequate flow and lighting, maintain proper water parameters (cal 400-460, alk 7-10dkh, temp 77-81, ph 8.0-8.2, salinity 1.024-1.027, and of course the lower the nitrates and phosphates; the better which can be achieved with proper filtration and weekly 15% water changes) as well as keeping them stable. You may also try dipping it in Coral RX. I have used amino acids in the past with stressed sps corals and would like to think it has helped them. Those corals were frags and have since then encrusted to their plugs and shown positive growth.