Well, if they're really sex linked, the males will have a white or cream spot on the top of the head when they hatch, and the females will have solid colored heads. The head spot is part of the barred pattern. So, don't need to go by combs, just go by head color!
Any pics of the "rocks"?
I think the barred birds are marans. The leg color looks more marans, and the chances of a white rock hiding barring but passing it on seems very remote to me. I think you just mis labeled eggs.
But let us know how the next hatch goes. And maybe post pics of your white rock hens?