Hognose stomach issues advice

I need some advice on what can cause diarrhea, weight loss and vomiting in hognose snakes other than low temperatures and parasites.

I have a hognose snake that is almost 2 years old that was purchased last April. She weighed 16 g when I got her and everything was good until the beginning of this year. She has always been a good eater, but over the winter she started refusing meals every other week. When I took her to the vet, they were not concerned.

Over the next two months I noticed she began to lose weight. In mid Feb, she regurgitated a mouse. I fasted her for two weeks and bumped up her temperatures, thinking the issue was because it was getting down to 68 degrees at night. A few weeks later I noticed she was pooping more often and I would find 4-5 poops in between meals. I scheduled a vet appointment but before we could get there I caught her vomiting on camera. She went through the motions of throwing up but only a little bit of clear liquid came out.

I got her to the vet that day and after an examination, the found she was underweight and dehydrated. She had at one point gotten up to 34g but was back down to 19g. They gave her some IV fluids and told me to make some changes in my husbandry.

I removed the Aspen and put her in paper towels so I could monitor her more easily. I also bumped up her temperatures - her cold side is 77-79, the middle is 83 during the day and 89 at night, the warm side is 91-94, and her basking spot is 95-100. These temps are achieved using a basking bulb and CHE controlled by a herpstat.

Since the vet visit over a month ago, she has thrown up 2 more times - both times there was nothing or very little clear liquid that just left a small damp spot. She was tested again using a fresher fecal sample but it was still negative.

My vet is at a loss. I am contemplating taking her to a different vet, but I wanted to reach out to this community for advice on what else this could be.

Other information -

She is in a 20 gallon long for now. I did cave and put her back on Aspen as she was very frustrated and stressed on the paper towels Her humidity is around 27-42, but mostly stays in the mid 30s. She has access to a humid hide on her cold side and she likes to sleep in there at night. She has a UVB light - Arcadia shade dweller. She has two hides, one on the cold and one on the warm. Get warm side one is a cave that doubles as her basking spot when she sits on top.
She has access to fresh water. I use reptisafe as a water conditioner. She is offered a f/t mouse every 6-7 days. I usually get my mice from rodentpro but the last batch came from cold blooded cafe. They sent rat pinkies instead of mice and that is what she has been eating (2-3grams). I was soaking the pinky in tuna juice to tempt her when she wasn’t eating regularly over the winter. I did not use it last feed. For a few weeks after she regurgitated I put nutribacdf on her mouse to replenish her food bacteria. She hasn’t had it in a few weeks. To rule out the batch of food from cold blooded cafe, I switched her back to a mouse pinky from rodent pro last weeks. She still vomited and had diarrhea after digesting it. I have 2 other snakes (sand boa, kingsnake) and 2 lizards (bearded dragon, crested gecko)

I would appreciate any advice you all have.