Good point, but the OP believes the birds to be around 6 weeks of age. Even if 15 weeks of age, comb color and size is a big indicator and often your first and best indicator. Hens don't get comb growth and color until point of lay, which for most breeds is about 20 to 24 weeks.
This much comb...
Not seeing any in the feathers. In the photos all feathers still look round and full. Saddle feathers are narrow and pointy.
More telling is age and comb size/color.
How old is the bird? If only 10 to 12 weeks, then you likely have a rooster as hens get red combs at point of lay.
If older bird...