I love star fish and I've tried to keep them for years
As others of our forum members have posted, some of these creatures do well and others will fade away for seemingly no reason
The problem seems to stem from the lack of research provided about what they actually feed on so tough to tell what we're doing wrong - or right ?! in order to help them thrive
I've got a red star now that I've had for about a year and he's/she's doing well - I guess !
Moves around a lot anyway, which is how I gauge the success (or not)
I've lost plenty of these creatures along the way but I don't think that a reef rank is complete without them !
Sorry that I couldn't be of more help
The only advice that I can give is to remove them immediately if you start to see their "innards" get expelled. They will quickly pollute your water chemistry if they die and you could lose corals