I was going to say that was a little young and shouldn't need to be aged for long.
So what color do you have. In my Manchurian Golds and Jumbo Browns I can start telling the difference just after they turn 2 weeks. Colors start changing, speckles start showing. The M. Golds are even easier, the males heads are darker and as they grow their chest colors will verify your guess. I like quessing at hatch.