Upside down swimming larvae

So, i got 3 larvae from a member here a few weeks ago. they all were awesome. all 3 are in their own container. i change the water daily, and feed them daily. today, i noticed one larvae swimming for a second, then stopping. when he stopped, he would kinda start to float up and tilt, before swimming again. this repeated over and over. figured he just got some gas in him from eating, no biggy. but i checked on him a little later, and now hes swimming upside down. i feed them blackworms, and i change the water using water from my already set up and cycled tank housing my two large axolotls. i also have some hornwort in each container for cover and improved water quality.

i dont want to lose him, cause hes grown so fast and hes already got quite the neat little personality, but i have no idea what this is or whats causing it.

thanks in advance.

updated: i lowered the water level significantly so he doesnt float as much. he seems not to be so upside down, but rather, sometimes sorta sideways. i also feed him more (he never refuses food) and gave him part of a wax worm (which he thrashed around eating)... i saw feeding them more can force gas out or whatever, so im kinda leaning this way.

my chinese fire-bellied newt had trapped wind once, and it was bobbing around upside down/sideways like that. I lowered the water level to make him more comfortable and he was back to normal the next morning.
Maybe the change from sideways to upside down was due to the gas moving down his gut?
Anyway, I hope he's feeling better soon x