I have 6 1 week old chicks, that I bought at 1 day old and bought 4 more today. The 4 new chicks are the same age but they are a lot smaller then the ones I had. What would cause this? Could it be because some came from a hatchery and the others came from a hobby breeder with fewer birds. Can someone give me some input on this or what they think might cause this. The darker silkie is one I've had for a week and the lighter silkie I got tolnight. Please help.