Help with dying Sarcophyton

My sarcophyton has not opened in the last 3 or 4 days and this is not normal for it - usually opens everyother day or is open 2 out of 3 days.  Everything else in the tank is doing great and all water params are great.  I took him out to inspect him closer and found a small star on the base so I rinsed the base rock with water hoping to kill anything bothering him.  Anyone know if these are harmfull to Sarcophytons?

Today the sarcophyton is finally shedding it's dirty mucous layer and is starting to look better.  I was a little premature to assume it was dying  I know that they do close up and shed but this time it was taking longer than normal.  I have heard of predatory worms that feed on their flesh and I have pulled a strange worm off of my Sarcophyton before so I am alway nervous when it does not look good.  I knew the star was not an Asterina, but since I didn't know what it was I thought it was better to be safe than sorry.  So, now it turns out I am the murderer of innocent little brittle stars. :-(  In my defense though when I saw the little guy the only thing showing was the arms that looked like some kind of worm, I didn't know what it was untill I rinsed it in fresh water and pulled it off.