How long do Plymouth Rocks lay pullet eggs?

[keystone]

I'm curious how long Plymouth Rocks lay the small pullet eggs before they lay the larger egg. I have 2 Buffs and a RR that are the same age (23 weeks) as my Rocks but are laying the full size egg. The Buffs and RR have been laying for about 3 weeks. The Rocks have just started laying pullet eggs the last week or so. Not a big deal but I am interested in this discrepancy between breeds.

 

[chickencoop789]

I got full sized eggs from my Rocks after about 3 weeks of laying. My RIRs and BRs started laying full size eggs at around the same time.