Corn snake not growing

Here she is, on a 24 oz Starbucks cup for size.

Have you taken her to a vet for this? I wonder if she has a metabolic disorder.

Kind of stuck with that front... I have not found a good reptile vet in my area (have taken other reptiles and amphibians before to different vets) so unless this is a super simple problem do not have confidence they can solve it. The other problem is no food in means no waste to test...

I am going to keep offering her food and may try moving to a smaller opaque tub to see if that works.

Smaller food, heated extra hot, in a small container in the evening is often effective for picky babies - it might work for your girl too.

While a fecal wouldn't be amiss, a blood test is what they would use to check for metabolic issues