Iris looks like a rooster to me. Time will tell for sure. I agree about the dark brahma/light brahma mix. I have 2 dark brahma girls and my girls have the same feather pattern as your chickens but yours are a lot lighter. They are beautiful birds though! I am still in shock on how pretty they are!
Tulip is a definate pullet, no doubt in my mind. Iris has me a little worried only because of her comb size. It is a little hard to see from here. Could you maybe get a better picture of her comb? All chickens develop at their own rate so I wouldn't worry too much about Tulip feathering out...