Those feathers look pretty round to me, I would say it is a pullet, they should be pointed by 18 weeks. I think all of them are pullets. It would have been cool to have a breeding trio of blue amers but I don't think you have any roos. Purely poultry sells blue amer cockerels for around $19 but they are out of stock right now. Also, I would expect to see some more comb development at this age in a cockerel, even if it is a amer.