I have 4 adult hens. I think that 3 of them are 2 years old, and 1 is 3 years old. They all lay well. But their eggs are so huge! I absolutely adore the gigantic eggs! They are twice the size of the pullet eggs I get. So, it seems to me that laying less has to be taken in conjunction with the size and weight of the eggs that they lay. Even if my pullets laid twice as many eggs as the adults, it would still come out even, weightwise. If that makes sense (?).
I'd keep them. At least until you know for certain that they aren't pulling their weight.
I'd keep them. At least until you know for certain that they aren't pulling their weight.