Did you order all pullets or straight run? It sounds like you have a roo in the bunch.
When I got my six pullets last week, I noticed one was a bit more aggressive than the others. Joyce was chest butting the other chicks and was always the one at the highest spot in the brooder.
Today, four days later, I noticed Joyce had considerably larger feet, and thicker legs. It dawned on me that I had a rooster!
When I took Joyce back to the feed store, they confirmed it by clasping Joyce by the head, and letting his body dangle. A rooster flaps its wings and fights back while a pullet will just meekly hang. Joyce fought in a fury of flapping and feet pumping. Luckily, they had just had a call from a customer wanting a roo of that breed, so Joyce was going to get a good home.
But it wasn't easy turning him in. We had bonded, and Joyce refused to stay in his box during the car trip, choosing instead to ride in my lap. I'll miss that fierce little six day old roo.