One of my hens is loosing her feathers - please help

We have 4 hens and have raised from chicks. They are about a year and a half old now. Within the last week, I've noticed that one of them is dramatically losing feathers around her body. I don't know what the problem could be or what to do. The other hens are as healthy as ever.

The one losing the feathers is still getting around fine with no noticable problems, but she looks scraggly and I'm worried about her as we are heading into winter now.

They usually eat laying pellets and I occasionally mix in some ground mix with corn,etc. They never do without constant food and water availability and I let them out to cruise the yard at least one day a week, sometimes several days a week.

I'm attempting to put pictures up. Any help will be appreciated.


The group.


Rosey and Cheepay. They should look like twins.


Their home.