Possible a small crispa or malu anemone?
The Nem has lost the algae inside it during transport/import, it will gain a goldenbrown colour as it regain them. It's normal for them to get rid of the algae to control their inner chemical balance and they need time to both sense how the balance needs to be in your tank and then build it up for that new location.
As already mentioned above it needs food during this period, more than otherwise needed.
I mince fresh meaty seafood into some left over mineral additive and some water from the aquarium and turn off the powerheads and blow the water-cocktail on the anemone with one of those plastic basters.
That way you can give it really small pieces that doesn't take as much energy to digest, most people say feed it every two days until it regains colouration.
After it regains colouration it can use your light to gain energy but right now it basically can't.
When you said it moved a lot, did you mean it moved location or that it moved the outer skirts more?
