I am only aware of one hobbyists who has managed to keep a feather star very long, over a year. This is so rare, that the world expert in these animals (crinoids) is interested in knowing how it was done. It appears to require a very large system, with many inverts, particularly urchins, continuously spawning. They are very difficult to feed in that they require very specific size food; mysis, etc is way to big for them.
Please ask your LFS to take it back, and not order them in the future. This has nothing to do with your abilities...they simply are virtually impossible to keep. Please, please, ask them not to carry them any longer. They take months to starve to death, in most cases.
Basket stars, and sterling is the expert here in the 'true' basket stars, are more likely to survive, but require intensive hands on care. They will become absolutely huge, over time, and I do not recommend they be kept.
Certain smaller hitch hiker 'basket stars' are easier to deal with, however, it is not likely that microvert would be enough alone. Odds are they were eating other stuff in the water too. Generally, I do not recommend them.