It is too young to tell gender. I'd post new photos when they are about 8 weeks old. By then, the cockerels will be developing larger, redder combs than the pullets (usually).
Only a few breeds can be sexed by their wing feathering, and that happens when they are a day old. As birds mature, they can also be sexed by the development of pointed sex feathers in the saddle and hackle area. However, the pointed feathers can take a long time to appear, and are not the most reliable method of sexing young birds.