I just noticed this morning that one of my hens has feathers missing around her vent. I do not have a roo and my girls do not peck at each other. As a matter of fact they get along very well. They are six months old and I believe most of them are laying eggs at this point. She is eating, drinking and acting fine. We have had very warm weather here for CT, it was 67 degree just a couple of days ago, but has become in the 30's - 40's the last day or so. The coop, run and nesting boxes are very clean and dry. The other girls seems to have full feathers. What could this be? Does it have anything to do with her being a new egg layer? Here are photos I just took. Any advice is greatly appreciated.