Just what do you mean by "a few of the stars?!" It is important to understand the seastars are very delicate critters, and water quality must be very good to keep them in most cases. Osmotic imbalances can cause these problems, and it may not be a good sign. In order to get some ideas, could you please answer the following:
How old is the tank?
What kind of stars do you have, if other than chocolate chip?
How long have you had these stars?
What are your exact water parameters, especially pH, alkalinity and specific gravity?
If you purchased them recently (within a month) how did you acclimate them?
What are you feeding them?
What kind of fish do you have?