You said you just lut it into the tank? Did you acclimate it properly, it sounds like stress to me! But Feather dusters are actually known to throw thier heads from time to time, either looking for better flow for food or maybe just not happy with the spot they are in!
I have a couple and my clowns have bonded, it agravates the dusters so much they spit off thier heads and the clowns follow it all over the tank! It's actually very funny to watch them trying to lay in it as it rolls with the flow!