I would go back and analyze what each of them looked like at hatch. That will help you a lot. Take a picture of each chick at a day or two old and then use those pics to help cull and choose breeders when they are older. I don't care what a cock looks like as a teenager if he was yellow or too light as a chick. And I can tell you from experience that their down color IS NOT an indication of how light or dark he will be as an adult. I no longer have lighter down males but when I did I grew them out separately. It was amazing that as adults there was no color difference. If you want to perpetuate the auto sexing easily then do not breed the lighter or yellow chicks no matter what they look like as adults.