Where did you get the Ams from? If they came from a feed store, they are most likely Easter Eggers. Ameraucanas are bred to SOP, and would have been sold as a specific color, and they would have cost you a LOT more than you paid for the PBR. Ams usually can only be bought from a breeder, while EE can be bought at feed stores, and are even erroneously mislabeled as Ams by the hatcheries that supply the feed stores.
The only reason I bring up this distinction is that EE IME often start laying fairly soon, while AMS take longer to mature. My EE are often the first pullets in the flock to lay.