I just put a featherduster in my tank yesterday. It has come out of its tube and buried itself under the sand. It has a wierd film growing around a section on the feathery part of its body and half of the crown is flowing but the other half is kind of laying on the sand or flowing against the sand. Is it dying? If it is just growing back its tube, what can I do to help it? Is there anything I can do to prevent it from dying?