First time with chicks and chickens in general. We picked up 8 chicks. My first question is a couple of them have some poo build up on their butts. What causes it and what is the best way to remove it? Second I've been tossing around the idea of getting a rooster also. We had these chicks for a little over a week. Would it still be ok to add a rooster chick to the bunch without too much trouble? Thanks