Really... That sucksssss I'm really unlucky when I get young chickens like this I already got two roosters I have to seperate I can't have this one but your saying the two black ones look like hens? The tiny black one is no bigger than my hand I'm guessing it's a bantam ??
I didn't realise the black ones were two separate birds, but in any case they both look like pullets. When you are buying chickens that are "off the light" (i.e. fully feathered, so approx 6 weeks old) avoid anything with a large red comb, large feet and legs, kind of lanky and tall in appearance. These are all cockerel traits. I'm not sure if that's a full barred rock cockerel you have there but for future reference note that with barred rocks the paler ones are male, the darker ones are female.