I put up heat lamps in my coop a few months ago and I recently noticed that one of my hen's tail feathers were a little burned about half way down. It has been a few weeks now, and the feathers are not growing back. Is there something I can do about it to get them to grow back, or is it permanent? (I have heat lamps in the coop because it gets below freezing at night where I live and one of my girls is molting.)