I have what i thought was a pure breed of dark cornish. I have a rooster and 4 hens of laying age and some younger ones. I just hatched my first batch. the chicks are yellow with black stripes down their backs. I expected them to be all black and have a few lighter spots. They look like some Americana's that I hatched years ago without fluffy cheeks. Should they have been all black if they are true bark cornish?