Is something wrong with my kitten?

She is 17 weeks old or so and idk if it's just me or she looks thinner. Everything is normal plays, eats, and poop is all normal. I am going to post some pictures that unfortunately r too blurry but she won't stay still. Is it just in my head? Could it be worms? Or is it a phase of growth they go through? Please please help I don't want anything to be wrong with her.

Excuse the pee on this one my sisters puppy was here and for some reason he always marks that same spot beside my bed (bad Sammy!)

Adolescent kittens do tend to thin down as they grow toward adulthood. They lose the baby belly. How often is she fed? You should be able to feel her ribs, but not see them through her skin.