losing feathers only on her back?

[ShadyChicks10]

I don't think she's molting (sp?) she has been losing feathers only on her back, all the way down to her skin. It'll seem to grow back but then go bare again. All the hens including her seem fine otherwise as do the two silkie roos in the house. What could this be, it doesn't look parasitic or bleeding...any help is appreciated

thanks

 

[Chickoneous Fry]

Possibly the roo's mounting did it to her. It's happening to mine right now so I am working on a chicken saddle to protect them until there feathers grow back fully or the roo is gone.