Feather Duster
 

My Sail Fin tang and Fox Face are picking at my feather duster. Does anyone have any suggestions on what to do to keep them off. Will it kill it if they keep picking?

If they continually keep picking at the feather duster and stressing it then yes it will die. It looses its crown and it will come back after some time however if this happens a lot and there is still a lot of stress it wont come back at all.
As for keeping them from picking at it; i dont have a clue

Maybe start feeding heavily at the opposite corner of the tank, so that the fish associate food with that corner as opposed to where your duster is located