They look like Mesenterial Filaments IMO. Pretty much the corals guts. Sometimes these are expelled as a defense mechanism, other times it could just be an indication that the coral is stressed out for some reason. What are your parameters? Are there any other corals close by?
There is a dunkin about three inches away. I did move it yesterday, from a bright area of my tank to the current place. It didn't seem happy in the brighter light.