I have 6 white leghorns that are 7 months old so roughly 28 weeks old. I got my 1st egg from them back on Sept.22nd and have been getting eggs every since! I think they were exactly 19 weeks old. I get 5-6 eggs from these 6 birds every day and they are ALL Large or Extra Large except... every day I get ONE medium egg. I assume it is from the same bird. My question is why? and will this bird always lay medium eggs or will they eventually become larger?