I would like to buy some leg bands of different colors to identify my girls. I only have 7 but would like to be able to easily identify who is who. They are 2 1/2 weeks old right now. What size band would be appropriate for them? I know they would have to be changed frequently as they are growing so fast. But which to start with now? Oh, and any guess as to what breed they may be? I'm clueless as they came from a Tractor Supply store. Their picture is my avatar. 4 black and 3 yellow.