I have 4 baby White Plymouth Rock chicks. They are about 9 days old. When they first came, they behaved like regular chicks. Now they are starting to try and fight eachother. Does this mean that some are roosters, or is this natural chick behavior? I haven't had chicks for 2-3 years so I'm not sure if this means anything or not. Is there any way to tell for sure if my chicks are male or female?