Axolotl sick with a few problems

Hi guys my first post here:happy:, it all started with my axolotl( Frank) stop eating with no other visual problems so i waited about a week trying to feed him but i haven't had any success, i then decided to fridge for a week and still nothing.

Then a couple of days later his tail started to float and then the next day his whole body , so back to the fridge he went, i brought him out of the fridge today and i noticed that he has what looks like air bubbles under his skin but it might just be in his stomach and also like red blobs on his tail which look like blood.

i have no idea why this has happened as i always clean up waste, do 25% water changes every week, i use sand on the bottom of my tank and feed him frozen axolotl food called axolotl food and earthworms.
i checked the water parameters and it came up with ammonia and nitrite as zero, nitrate as 0-5mgl also ph is 7 and water temp 16-17 degress

if anyone can help it is much appreciated thanks:happy:

A photo of the red blobs and the side where you can see the air bubble would be helpful

i went to take the pictures just before and i found frank upside dead
i dont know what went wrong but im pretty guttered with the lost of him, he was swimming around about an hour ago then when i came back he was upside down floating and no movement at all

It sounds like it might have been an infection of some sort. If he went that quickly, there probably wasn't much you could do. Salamanders don't show signs of illness until they're already pretty sick, so don't let it get you down too much.

I know what it's like, and most people don't understand. But you grow pretty attached to the little guys. I'm sorry for your loss.