I do not see any pictures, so maybe try adding them again? I think that you may need to have ten posts before you get the ability to add pictures.
However, the breeder is wrong in saying that there isn't a good way to tell if you have a pullet or cockerel before they crow or lay an egg. In most cases, a rooster will get a larger, redder comb by the time it is eight weeks old. At the same age, a pullet's comb is usually almost non existent and a pale color. Roosters get pointy hackle (neck) feathers and saddle feathers (the longer pointy feathers near the tail--hens don't get them) by the time they are four months old or so. A hen has blunt hackle feathers, not pointy. Also, a rooster gets sickle feathers (the long feathers on the tail). These take a longer time to grow in, but you should start seeing these by the time they are five months old or so.
Edit: While I was typing, you must have added the pictures. I see them now. Your Sussex and Buff Rock are both roosters, but your Hamburg is a hen.