I have six 9 week old chicks in my coop and I have six 5 week old chicks in my brooder. at what age can I add the younger ones to the coop with the older ones? also what can I expect and what should I watch for? I am new at all of this. The 5 week olds are a lot smaller then the 9 week olds and I am scared the older ones will kill the younger ones.