If I buy 7 chicks, and vaccinate all of them, can I add a non vaccinated chick, or two to the brooder? I ordered 7, but two of the breeds I wanted were not available, so I might buy them from a farm, or people I know. Would it be ok to do this? Could I vaccinate them if they are more than one day old, because someone on BYC said they vaccinate birds of all ages? The vaccination is Marek's by the way.