What did your barred rocks look like when they first started laying? Mine are 21 weeks old. Their faces are red, but they have small combs and waddles. I'm just curious.
A well bred Barred Rock won't start laying until well after 30 weeks.
The genetics of the true bred Barred Rock will only allow the maturity to move so quickly.
Hatchery Barred Rocks often lay much earlier, somewhere around 24 weeks, but this comes at a cost to crisp barring and true Rock type in the body. They've snuck a lot of Mediterranean blood in there, to speed everything up.