Big fat balls

Sometimes you see really husky balls and some are thinner.
Mine has been a good eater, she looks kinda skinny though.

Is it a juvenile thing or a breeding difference?

Each one grows at its own rate just like people. Some will get longer quicker than others while others will get thicker but stay shorter while on the same diet! Nothing you can do about it. As long as the snake is eating proper size prey regularly with the occasional going off feed for a while they will be doing just fine.

From what I've read about captive snakes, better to maintain snakes with an "athletic" build* rather than tubby...obesity is bad for an animal, reptile or mammal...=)

*I'm a noob still, so please correct me if I'm wrong. I'm not a snake breeder, so there is probably a different strategy for females going into the breeding season. I have pets. =)

I'm always worrying about it with my snakes...and then I see an overweight snake and think "ah...yeah...my snakes are fine", hehe.