My pineapple mint has produced beautiful leaves but perhaps two variegated ones only. Why?

I grow it in a pot, full sun. Is it too much sun? I read somewhere that variegated plants react to the amount of direct light but don't remember if variegation became more marked with more sun, or the opposite. Do you know?

My pineapple mint has produced beautiful leaves but perhaps two variegated ones only. Why?
On the plants that I grew, the smaller leaves usually had much more variegation on them that seemed to fade as the leaves matured. The more sun that the plant gets the less variegation you will have. Also if you have other mint close by you can have cross pollination which may cause this also.