The chest definitely indicates silver laced wyandotte, but the comb and other coloring are from another breed. My guess would be the welsummer. He's a handsome "mutt" regardless.
According to the 4sq. ft. per bird recommendation, an 8X8 can house up to 18, so your 15 will use quite a bit of your available space anyway. They will be just fine.
It is a bit common, especially in hatchery birds, to get an occasional single comb. I believe the first one is a pullet anyway. If you could show a pic of the body of the second in question, I could probably give you a better guess, but I am thinking that one is a pullet as well.