Do a water test and post the results. maybe we can help you figure out the problem.
Do the full gamit, pH, calcium, phosphate nitrates, alkalinity, salinity, salt that you use and temperature.
It's been awhile, but the polyps have been out. But it was the first time they haven't been out for over a week since I got the coral in 2011. I will have to get an updated pic to share.
Suspect that's just algae formed over there. My toadstool had that for months. I cleaned it with an old toothbrush -- not sure f that was s good idea or not...