No weight gain

I can’t really understand how it’s possible but my corn snake Molly who’s a couple months old isn’t gaining weight. When i first got her she would eat a pinky from forceps and seemed like a good eater, even taking two on her third feed. On her 4th feed she acted afraid of the pinky and wouldn’t eat. I waited a couple days and left one in her viv overnight and she ate it. She hasn’t ever gone over a week without eating, but refuses occasionally and never eats more than one. A few weeks ago she weighed 17 grams and i weighed her tonight at 16 grams. She appears to be healthy, she usually comes out to roam when the sun goes down and doesn’t mind handling, but the weight gain can’t be okay. Any ideas as to what could be wrong??