Illness/Sickness: Major loss of appetite!

My year old axolotl was raised on freeze-dried worms, which I was hand feeding him. A few months ago I realized they aren't the healthiest option, so I tried switching up his diet. First to frozen worms, then live earthworms (which I am rinsing thoroughly and cutting into small portions). Now, suddenly, he won't eat. Anything I try to feed by hand, even in desperation his old staple of dried worm-cubes, he completely ignores, and while he initially gets excited by the live worms and eats them off the tongs, he always spits them out soon after. I'm getting very worried as he is losing weight and I have run out of food ideas. He's had sand as a substrate his whole life. I have never kept him on gravel or put small, swallowable items in his tank, so I can't imagine him being impacted. The tank temperature has always been kept around 68 degrees. He is still as active as he's ever been. I can't think of anything else that would have caused this sudden change. He hasn't eaten a meal in almost three weeks now.. Any advice you have you be appreciated, I'm so worried for my little fella

Since he is losing weight, that is a reason to worry.

When my axies lost their appetite last year and refused to eat, it turned out they had an internal protozoan infection. I don't believe that is a common cause, however. A vet can diagnose something like that with a stool sample (which is hard to get if axie isn't eating.)

Some other people have had success tempting axolotls that aren't sick (just not eating for whatever reason fits in their little brains) with things like prawns, blood worms, black worms, and other "treat" food. When mine were sick, I could still get them to sometimes reflexively snap at (and sometimes eat) falling pellets.

Is there a good vet that treats amphibians in your area? If he is sick, and not just trying to stress you out, a vet will be your best bet in getting a proper diagnosis and treatment. Ask questions though - some vets treat axolotls like reptiles, but some reptile-safe medications aren't axolotl safe.

Thank you very much for the advice. I'll look for a vet, and in the meantime I bought prawns. Maybe a stupid question, but should I cook them first..?

I second that recommendation. Even though our female is big and chunky, when she turns down a worm I immediately start to worry. But I've never seen her spit out a frozen/thawed krill. No to cooking them, btw.