I have a Buttercup in similar shape. Brought her into the garage tonight since we will be in single digits tonight.
No rooster here, 16 chickens. Many of them have lower back feather damage and I'm trying to alleviate boredom.
But this one Buttercup I picked up this morning and all of her belly feathers are missing, neck feathers, and back feathers.
When I put her down a puff of additional feathers just fell off so I stated to think that it might not just be plucking.
I'm bringing her into work tomorrow afternoon to see one one of our avian vets and I'll keep you all posted.
Can this possibly be molting in January?? It's in the single digits here, and has been cold for several weeks!