Susanne, I have seen that on my trees. It occurs (as it has been explained to me here) because the tree has lower light levels and the larger leaves are an adaptation to the lower levels.

This is a bit what I expected. But it must be more to it then the light?? For example the variegated lemon was in full sun this summer when put out the big leafs and then got smaller leafs. The ST Feminello made two huge leafs shortly after coming inside and now without changing lights, is growing normal sized leafs. Just makes me wonder how they decide what to grow.

I've wondered the same thing. Every citrus I have, has one or two giant leaves mixed in with mostly normal sized ones and one or two tiny ones. I've long assumed the tiny or misshapen ones had to do with not enough water when they were growing.