I have 5 seven week old chicks in a 8 x 12 pen and 3x4 coop. I'm new to the whole chicken world but I wanted to get a Rhode Island Red mixed in the group but she is 9 months old. Would this create a problem with the others or are they young enough where they just wouldn't care? I'm not sure of any other information that may be needed to determine if this is a good or bad decision but any response would be much appreciated.