hen bald spots, no rooster

[Tracyree]

So I have this hen that has bald spots on her "shoulders" (where her wings start) and some on her back. I don't have a rooster. I have 8 hens and a very large run. I haven't seen anyone picking on her, but it's not out of the question.

Could it be a hard molt or is it more likely that the other hens caused her problem? I'd be blaming a poor innocent roo if we had one as it looks exactly like over breeding.