We have four whites. We bought two of them at the same time and one has grown and the other hasn't. We assume that the two youngest are about 9 months or so and one has grown as large as the other three and one is about the same size as 'she' was when we got them. She has the healthiest and most social, is chubby but just never gets any bigger. Is there such a thing as a "dwarf" White's? Thanks!!