Holy bristle stars batman!

So normally my bristle stars just stay in the dark and have there arms flail around like a hentai waiting to happen. But lately they have been crawling all around the tank and I'm noticing that there centers have large yellow holes. Some of them have even split into two. Is this normal? It doesn't look normal and I can't really find anything online about it. Here is a picture of what it looks like. It's the same on all of them. Possibly a bacteria?

 

I would for sure test parameters.

When you seem them out like that they are either spawning or stressed.

 

....yes, test for certain...got some GHA going on thre as well..so, I see a few "mini Brittle Star fish" as well as a pretty good size "Bristle worm" ..did you just feed? ..if not, it is rare to see either of these guys out and about..as you stated. ..the yellow that I see on the brittle stars is unknown to me..I am looking into it as well..starnge..I have hundreds, and have never seen such a thing on them.?? But, as stated earlier, test things and see where your at and post it. I am curious.

 

looks like they popped their tops

brittle stars and serpent stars tend to over eat and it will pop the top right off them, it can also happen if the salinity is not right.

have you checked salinity? is it possible someone in the tank is missing and become a feast for them??
possibly fed them too many treats???
the best thing is just to leave them as is and make sure parameters are correct.
if salinity is out adjust it back slowly. stars heal quite well.
just make sure they don't have any unnessesary stress.
i had one pop a top once and was sure he was a goner......he's fine and growing strong now
good luck!!

 

Thats a trip...never heard of it ! : )..lol, pop a top ! love it...good info. : )