HELP! It’s my first Axolotl..

So, 5 days ago I bought an axolotl, his name is Toothless (I know cliche but my fiancé picked it out) and I’m super worried. He hasn’t eaten a thing (he’s a juvenile not even 2 inches long) I’ve tried pellets, flakes, frozen bloodworms, frozen krill, live earthworms, live night crawler, live mealworms, and I’ve even tried a carnivore blend. Nothing. And now he’s floating. He has been for 3 days. I push him down into his plant but he has to come up for air and then can’t get back down. I’m freaking out. I have 5 reptiles, 4 cats, a pit bull, 2 rodents, a beta sorority and now him. I go above and beyond to do anything for my animals I just don’t know where to turn here. I’m so scared, and my pet store hasn’t helped at all., Prior to getting him I set up and cycled the tank. Temp has been at 18.3c and highest at 19.3 today. No traces of nitrate or nitrite, ph is stable, ammonia isn’t a problem, and the hardness is perfect. His water is absolutely as perfect as It gets. I have a low flow filter that’s adjustable and he’s in a 10 gallon tank. I’m using a very fine sand substrate, with plenty of hides and 2 plants for him to play in. Please help. I can’t watch him like this anymore, I really need someone.

Axolotls tend to have high death rates at young ages, so since it is two inches, it is hard to tell if it is/will stay in good health since it is so young. It's best to buy axolotls when they are 3-4 inches so you know that they don't have any defects or health issues/potential problems. i hope everything goes well for you.