I've had heritage breed pullets start laying at 16 weeks. I've had them not lay their first egg until 9 months. I also try to avoid blanket statements, With living animals you just do not get guarantees. Practically anything can happen.Has anyone had their chickens lay their first older than 27 weeks?
On top of everything else, you only have 3 pullets. That's not enough for statistical averages to mean anything. If you had 100 pullets the averages might mean something, but you still have a lot of other variables like the time of the year.
I also do not believe that calcium has much if anything to do with them laying early or late. If they are not getting enough calcium the eggshells will be thin but the rest of the egg should be there. If they are not getting enough calcium the thin eggshells can cause other problems so I like to have a calcium source like oyster shell available so the ones that need the calcium can eat if but the ones that don't need it aren't forced to eat it. Mine are really good at deciding how much they need to eat.
