It started about two weeks ago. I noticed that one of my Rhode Island Reds, who has had the prettiest dark red feathers, had what looked like a 'part' down the front of her chest--which looks like she hasn't had her roots done in months! Then I noticed that my largest BO is dropping feathers EVERYWHERE! Most are the tiny fluff feathers and her bottom is naked! They are looking really bad.. I looked for pest/mites etc and saw nothing..I dusted the nest box, roost and added some new dust to the dust bath... They are 18months old.. Haven't had chickens do this before..Only had them a little over a yr..