I'm not an expert but I had a similar problem, I moved the coral slightly to make sure it wasn't shaded by a shadow from my wave pumps, gave it a gentle brush with a toothbrush (to remove some algae which I had noticed beginning growing on it) and finally positioned one of the wave pumps to pump water directly at it. I also did a 15% water change. I have no idea what bit worked - I suppose thats the problem with doing everything at once (I just didn't want it to die) - it recovered and is now quite happy.
Don't ask what posessed me to brush it with a tooth brush! I'm not sure it was the sensibilist thing to do in hindsight but since my clowns brushed against it and a hermit lived in I I figured it wasn't likely to do harm provided I was very gentle.
I hope it recovers.