I don't have experience of EEs to identify sex at this age but that white one doesn't look like a leghorn to me and I would say it was a cockerel with that much pinkness in it's comb and those thick heavy shanks. I would have expected a leghorn to be smaller than the others rather than the biggest ,as that white one seems to be, and leghorn pullets have pretty delicate legs. Maybe it's a white Plymouth Rock, but it's one of the more likely cockerels in my opinion along with the RIR which is very obviously male