growth rates

[red bootz]

I've got two red foots, (named Sakura and Ume just in case you're curious) and their about three years old now. The thing is there both getting big, its just that one (Sakura)is growing at a much faster rate! I'd say hes about a good centimeter and a half, (maybe two) bigger than the other. I got them as hatchlings and they've been together for the whole time so the conditions, food,etc. should be the same. Any ideas?