It's really hard to tell when they're that young, or at any age for that matter. And they all develop differently, so the best advice I can give you is take good pics of your birds and post them for everyone else to see and put their opinions in.
Hi Jason. With Silkies sexing is very difficult, but there are some indicators to look for. The crest is different in male and females. In males there will be spikey feathers of varying lengths flipping back toward the tail. The crest of the pullet is usually a puffball will all feathers of uniform length. The shape of the comb differs (size of comb in young birds is not a very good indicator). The males comb is wide from side to side. The female usually has a thinner comb that is longer from front to back. Body form and tail feathers are other indicators that I use.