Obviously, I have not seen your chicks, so I don't know what stage of feather development that they are at, but I would imagine they are not fully feathered at 2-3 weeks. I have chicks in the brooder that are a week old today, and they only have wing feathers. Fully feathered would mean absolutely no down left on them, in my opinion. I'm going to guess that the first time I brooded chicks and moved them to the coop it was probably late May and they were 5-6 weeks old.
Do you have other birds in the coop, or is this your first flock?
Do you have other birds in the coop, or is this your first flock?