Blue Linckia Starfish Not Looking Great

I bought a Blue Linckia about 2 weeks ago.
I must admit, I wasn't full versed in just how difficult these were to keep.
I acclimated it for about 3 hours, and it seemed to be doing well up until yesterday.

It's just been hanging out on the glass for the past few days, but it looks like it's shrinking.
It also has these bumps on it...

I know that the standard line is that nobody really knows what they eat, but if it's struggling, is there anything I can do for it?

I've been careful not to have salinity swings, temperature level, etc.

Here's some pics:

 

Most likely needs something to eat, I can tell from looking at your tank that it will not support a linka.

 

How old is the tank? How big is it also? What inhabitants are in the tank?

 

Yeah, I wish I wouldn't have bought it.
Or the guy would have asked me what I had going on before I bought it.

Not support just because it's not established enough with "slime" and stuff for it to find?

If I gave it back to the store, would it work out, or what would you do?

 

Yeah, unfortunately, they almost always starve. The only exception may be a very large, well established reef. Even then it's hit or miss though.

 

Tank isn't very old, like i said I really wasn't fully prepared for what it would take.
Tank has been up and running for about 6 weeks.

As for inverts, they seem to all be doing really well.
I've got about 10 red-legged hermits, and 10 or so different snails.

Fish:
Yellow Tang
2 Small Clowns
1 Pink Spotted Goby
1 Foxfaced Rabbit

 

Taking it back may be a good idea. I don't know if it would be better off in the store, but it won't be worse off. Also, they may be able to find someone with a larger, older tank to get it to. The other inverts should be fine. Starfish are much tougher to keep.

 

How do you do that?

 

I have one and when the bottom of the leg is up like hanging off the glass in the water i drop pellets for the little things to catch.( I cant think right off hand what they are called.)

 

Some say film algae, some say bacterial film. Either way they need large established systems with a lot of LR and areas on the glass if possible where the film algae is not being cleaned away all the time.