Are my 3 week old Serama chicks pullets or Roos?

[CaliTexGal]

Can I get guesses as to the sexes of my 3 week old babies? I have included two photos of each so a total of 4 chicks. I think the second one (dark color photos 3/4) is a Roo. I am also leaning towards a Roo for the last one (photos 7/8). The lighter colored ones photos 1/2, 5/6 and 7/8 are silkied Seramas and the dark colored one is smooth feather photos 3/4 so I don’t know if that plays into their development as well. Thanks in advance!

 

[Tonyroo]

You have one cockerel.

 

[nuthatched]

The dark one with a comb is definitely a cockerel and possibly the one under it.