Got 6 chicks from Tractor Supply last week. They were in a bin labeled Columbian Rock Cross assorted pullets. The guy seemed to know a lot about chickens so I asked why it said assorted pullets and his reply was it should just say pullets. I bought them anyway (of course!). My question is, how do I tell? All of them look the same with their markings. They're now 8 days old.