I have the same paranoia! Some days I think Bulu's looking a little chunky and my friends reprimand me for being silly. Other days I think she's too skinny, and start spoiling her with mealworms.
She looks bigger probably because she is getting bigger. Since it's a growing process, you don't notice an abrupt change, but you just feel like she's getting rounder and longer. No biggie. The fat content in your mix seems decent. Some hedgies need an even higher fat content because they just run so much.
Anddd, she's still a growing baby, which means she'll need more food/fat. I think when a hedgie is obese, you'll really notice, and even then there are ways to help them get to a healthier weight again. Haha why do we worry ourselves pointlessly?