Is my anemone dying???

I bought a sebae anemone about 2 weeks ago. It was doing fine until yesterday it wouldn't eat. Also a little while later, I noticed it was unattached and hung in a rock. I gently moved to back where it was and a little while later it was again, unattached and hung in another rock. It has purple tips and is a tannish color on the tentacles. Its mouth is slightly open as well and I heard that was a bad sign. Water is perfect. I was feeding it everyday almost as I was told at the pet store they feed theirs everyday and if the tentacles are long its hungry. I fed a 1/8 inch square piece of salmon. Should I just expect the worst and hope for the best? I dont want to take it out early if it still has a fighting chance. Thanks.