I am not sure about yours, I think the first and last one are roos and the middle one is a pullet. I have three 9 week old silkies and one has a comb about the size of your white silkie and the other two have a flat wide area there, no comb yet. So I am guessing that means two pullets and one roo. I also have three 4 week old silkies and one of them has the beginning of a comb forming too and it is very cocky. So I think either mine are easier to determine than most, or I am being fooled beyond belief! Either way, I spend way too much time with chickens. LOL. They are too cute either way. My white one that I believe to be a roo looks just like your white one but he has some kind of neurological damage and his head wobbles side to side. He eats and does fine otherwise. But we call him Loopy! Thought it fit! I hope he gets better but I doubt it. But we will love him until he dies either way. Take care of those babies, hoping you have what you want!!!
Marie