Illness/Sickness: Please help :( newt can't swim down, floating around the tank

[AstroZombie]

I have a male alpine newt which is about a year old and have had him since he was a juvenile, all has been fine but just recently he has been floating around at the top unable to swim down, he has obvious signs of injury or illness that I can see, he just floats around. The first day I noticed a problem he was upside down at the bottom, trying to turn himself the right way round. He's not bloated by the look of him, he looks normal. His tail is slightly bent at the end, looks a bit crooked, that's new as well. Is that a sign of stress? The female alpine we have in there is fine. We also have 4 wcm minnows in there which have always been there. The tank size is 13gallon and we have plenty of plants in there and a turtle dock, also a gentle filter so it doesn't create too much of a current. We have sand at the bottom instead of pebbles too. I've attached a picture of him from the side of the tank, it's like he has a bubble in his belly and it's keeping him floating and not allowing him to swim down :/

He's fed blood worms and occasionally small earthworms.

Any help would be appreciated! Thanks in advance

 

[AstroZombie]

Nvm it's dead... Thank for the help tho.