Hi, I'm Kim from TN. I have a Small flock (so far) of Australorps, 1 Roo & 3 hens. However, My husband built a HUGE brooder for 3 (supposed) Barred Rock Pullets (but you know how it is at the Co-op re: sexing). Since this Giant MONSTER of a Brooder is occupying my Coffee table in the living room, it seems a shame not to add more, don't you think? Would it be ok to mix chicks that were just a few days old with some that are a little over 3 weeks old? Should I try to find older chicks instead? How and when should I introduce them to my 1yr old flock?