I need some help, I have 8 chickens of different breeds I am new at chicken keeping and need some advice before winter hits I noticed my chickens we're losing feathers I thought it was weird but figured it was molting I keep a heater in the coop so I wasn't too concerned they act normally eating and drinking fine. my dilemma is they are still without feathers I have one chicken who has a complete bare butt and has been this way for months I thought it's been too long for a molt I checked for bugs and couldn't find any on the birds I did notice one small white pin point bug on the coop itself so I decided to treat with sevin dust. I tested the entire coop and nesting boxes I changed the pine shavings and hay. I even dusted the run. I also gave them de in their favorite dusting area which they use quite often.the chicken that I have my concern with the most is my white chicken the one with the bare butt. she grew quite larger than all the rest of the chickens and she was younger than the rest. she also walks heavier and as of heavier chicken then the rest she has a bulge to her bottom and has always had loose stool. I originally had two of them but one died a few months ago of unknown cause.here is a picture of my white chicken can anybody help I need advice on what to do or if to do anything am I being over concerned?