Just a thought Annie, do you think your hen is eating feathers ? Methionine deficient feeds can eventually lead to this behavior. The hen will actually pull her s and others feathers in an attempt to satisfy her requirements. I would be inclined to add a poultry vitamin to their water once a week.
http://msucares.com/poultry/feeds/poultry_feathering.html
http://msucares.com/poultry/feeds/poultry_feathering.html