Ok, so I have four hens that free-range during the day and are in a roomy coup at night. The boss hen has been loosing her feathers steadily for the past couple of days. Her belly is missing the most ans she has a few other spots here and there along with rump feathers that are basically MIA. I checked her out and there are no bite wounds or anything else suspicious. All of the other hens are just fine. What could this be?