This is my first time to raise chickens. We have 9. Today I discovered this unfeathered area on the back of my Easter Egger. She is acting fine, eating, active. The area doesn't look irritated or bloody. It is missing feathers, and it wasn't like that 2 days ago. Grace is 9 weeks old. She has always seemed to be the most mature of the group, she was maybe a day or 2 older than the rest. They get along fine. I don't see any picking or fighting. I live in Illinois. We moved them out to a new coop that we built in our back yard 2 weeks ago. Before that they were inside our house. We haven't finished the run yet-planning to get it done this week. They eat medicated chick starter/grower by Purina. I give them chick grit also. I just recently started giving them some greens from the garden, grapes, meal worms, and some friends brought over a few slugs and worms from their garden. I don't over-do it with the treats, their primary food is their regular chick food. I'm really worried and not sure if this is an infection, mite, or ? None of the other chicks have anything like this. I really appreciate your help.