Hen missing feathers

[Lalythra]

I have 11 hens and 1 rooster. All of my other hens aren't losing feathers at this time. These chickens were all one year of age as of last month. One hen (black sex-link) has a totally bald stomach and an area above her tail that is scabby and mostly bald but with pieces of feather ends still in the skin. Any ideas? She's still laying eggs, not making a nest for going broody (as was suggested by a co-worker) and otherwise seems perfectly fine. Help would be appreciated.

 

[Lalythra]

As a side note, nobody has molted since shortly after we got them when they were still tiny.