I have 2 chicks who are approximately 4 weeks old. I believe one of them to be a roo. I'm now thinking I'll need a couple more hens (not looking for a boat-load of eggs, just enough for my family). Would I be able to get a couple week-old chicks and add them to the mix with minimal upset? The two I have are pretty tight with each other, as they're the only ones. I don't want any fighting, but won't it be easier to do now rather than later?