3-Year-Old Axolotl Barely Eats and Seems Underweight — looking for advice

Hey everyone!

I’ve had my axolotl for about three years now. I’ve had her since she was a baby, and I’ve always had some trouble getting her to eat consistently.

When I first got her she was a baby, and i fed her exclusively bloodworms and fed her every day and she was fine. She ate well. Once she was 1 year old I switched her to an adult diet (mostly pellets with occasional bloodworms as a treat), and feeding every other day. she was fine for the first little bit and then she started refusing food so I switched her to every 3 days. But over the winter she went through a period of a couple of months where she refused to eat and when she occasionally did, she would either chew the food up and spit it out or throw it up a few hours or days later. Ever since then she's had this problem. I tried feeding her smaller amounts more often, and I've tried feeding her less often (every 4 days) and there's no change.

This has been happening on and off for the entire three years I’ve had her. Nothing major has happened health-wise, and she otherwise seems to act normally, but I’m becoming increasingly concerned because she looks pretty skinny compared to other axolotls I’ve seen, and I can see her ribs.

Tank/water parameters:

• 20-gallon tank
• Aquarium sand substrate
• A few decorations/hides
• Temperature: ~17–18°C (usually stays between 15–18°C)
• pH: ~7–8
• Ammonia: 0
• Nitrite: 0
• Nitrate: 0

She seems to behave normally otherwise. She moves around when she’s active and is generally inactive/sleeping when she’s supposed to be. I haven’t noticed any major changes in her behavior.

I’m just worried because I obviously want her to be healthy and happy, and I don’t want to overlook something just because she’s been like this for a long time.

Does anyone have any ideas about what could be causing this? Are there any other foods I should try, things I should test/check, or other signs I should be looking for to determine whether something is wrong?

I’d really appreciate any advice. I just want to make sure she’s healthy and happy in her home!