I have a similar situation. I have 6 Isa Brown's, 2 white leghorns, 2 Buff Orpingtons, and 5 Wyandottes - all about 5 months old and beginning to lay. I have 2 older Easter Eggers and some others, but the young chicks are laying very small eggs. My older Easter Eggers usually lay large green eggs, but we have been through a dry spell where no one was laying - maybe the heat, but it began with very large chicken snakes eating our eggs. Anyway, I am getting small green eggs and cannot figure out who is laying them.????? I don't think it is my older chickens because the eggs are so small and about the same size as my other young chicks.