Is my green brittle starfish sick?

[empedraza86]

I purchased my green brittle starfish 2 weeks ago from a local fish store I go to regularly. He is a very large starfish. I have a 55 gallon tank which contains 1 yellow tang, 1 maroon clownfish, 1 emerald crab, 1 mushroom, & 1 shrimp. A few days ago i noticed that my brittle star has pink on 2 of his legs. It looks as if the green on his leg was rubbed off. I've checked him out & nothing has been eating at him. He looks perfectly healthy. He eats everyday because of his size. I have no idea if its my water levels causing this or bristle worms (because i do have those in my tank that i'm having to get rid of) or something else. If anyone can help me out PLEASE i would greatly appreciate it

 

[Holygral]

I have had 2 large b stars for 10 years, I would guess maybe a crab. Brittle stars have a pretty hard skin. Mine are in with a large black spiny urchin and have never had a problem, I had a rock lobster for years and he didt even bother the stars.