I had a bunch of white and black zip ties, so I loosely placed one on a leg, of several, not all, of the birds in question.
I thought that I had found proof positive, on a few of these youngsters, of being boys. when I found the same signs on a couple of known laying hens.
What I found, I thought was the beginnings of spurs. Little semi-sharp nubs, right where the spurs on a male should be. But, at least two of my red hens, have similar nubs, so I guess not.
Time, certainly will tell everything, but it would help to know, with certainty, before we start caponizing.