Here are my guesses for their genders. They are 4 weeks old on Monday.
red frizzle cochin bantam- pullet
black cochin- 50/50? comb is straight. no red. thick legs. no tail feathers. is the largest in the brooder. wattles growing.
porcelain d'uccle- pullet
mille fleur d'uccle- cockerel
A week later...Jack Black is for sure a little roo. He will be 5 weeks old Monday. It's interesting to watch him. He will sit and let others eat first..he usually perches on top of the red feeding bin while they eat. The others will be walking around scratching and he will sit down near them or he just stands still looking around. My other little roo doesn't do that.
Cute chicks-but they always are. As you have found out; birds are individuals-at least to some degree. The different breeds can act quite differently. I actually have a serama roo that broods chicks and helps raise them. Not a common trait.
I see this thread is a few weeks old--have the genders become obvious as they grew?
If not, post updated photos and maybe someone here can figure it out now