Fat dwarf african frogs

[frogwings]

Here are the pictures I took with my ipad.
The one on the left (and the middle) is the fat one, obviously, and the one on the right is the normal one? 3 of the frogs look like the fat one. The one in the picture (on the left) is about 6 years old and has looked like that for several years. The other 2 are just like her and seem perfectly healthy except for their size. So-o-o-o, what do you think? How do I put the fatties on a diet, or so I need to, and keep the little one from starving? Any advice is appreciated! Thanks!