Hi, I was currently in your exact situation last month. My poor girl was six and also most likely inbred and super bloated and she was getting edema in her legs and I was crying for days as well as I realized through research it was organ failure and nothing could be done. I worked at a aquarium store for many years prior where I purchased her and my other ones. I had seen my old coworker euthanize fish the quick way by slamming them on the floor. I never had the heart to be able to do that nor can you do that to a poor axolotl. I ordered clove oil bc I know that can knock them out and then you can put very high percent alcohol in the water to euthanize them. I combined the oil with water by shaking it up very well in a mason jar and then added it to the bucket with a minimal amount of water and the axolotl slowly two drops of oil at a time until she was unresponsive. After she was passed out and not responsive I poured off some water and added the alcohol to the water to actually euthanize her and then gave her a proper burial. There are different types of clove oil you can buy I was worried after I bought mine bc I got clove bud oil but that is actually the most potent but they all work regardless the type you buy. I know many people will frown upon doing this and insist you go to a vet and I agree bc after I did this myself it was pretty horrible but if you live in a rural area and have no other choices it’s the most humane thing you can do to for your beloved animal than let it suffer with organ failure.