Star polyps covered in ???

[got bait?]

I have a 5 x 5 in. rock covered with star polyps, but they are covered with something I have never seen before. I looks like cob webs, not green. Any clue and if so what will get rid of this. I have plenty of snails and hermits, but they won't touch the stuff.

 

[reefobsessed]

If stressed for some reason, mine will put off a whitish slim... I just make sure they are in a fair amount of current and it comes right off....

 

[got bait?]

I even went so far as to to brush them off with a new paint brush and they still won't open up. All other critters and chems are fine.