I bought a 7 week old white easter egger off of craigslist yesterday. The woman was real nice and told me that the bird was 7 weeks old. I have 7 5-week old birds in a brooder in the garage. I put the new bird in to meet the others but kept a mesh barrier between them. It was like this most of the day. I normally had a different bird behind the mesh barrier due to an injury. Well I wanted to put the injured one back in the main brooder behind the mesh so I put the new 7 week old in with my 5 week olds on the other side of the mesh. They are roughly the same size, 7 week old is a tiny bit bigger but not much. This morning one of my 5 week olds was limping around the brooder. I separated her and watched the birds for awhile, no aggression at all. Do you think the new bird is responsible for the injury? I am confused I don't know whether to blame the new bird or question whether or not it happened as an accident. Last question, at what point can I add my new birds to my 6 month old, basically full-grown flock?