I think my axie is sick! Please help!

I have an adolescent axolotl named Andrew. About 3 days ago, his tank was looking pretty disgusting, so I took him out, put him in a container of cold water, and proceeded to scrub the inside of his tank and everything in it. I try to only do this process about once every 2 weeks, (although I do a regular water change at least once a week if not more) as it's a bit stressful for him, but he's always very happy to have clean water.

So after doing a deep clean of his tank, I put him back and he swam around happily like normal. But the next day, he was acting a bit strange. He's usually quite happy and social, (i.e, he will swim up to the glass when I come to see him, he swims around a lot and is very active, and he loves to come up and nibble on my finger) but now, he'll stay behind his rock and hide under his water filter all day, which isn't that unusual, he likes how the filter feels, but he won't move the entire day. He'll only move if he has to go up and get air, and on that note, he seems to be struggling to swim properly. He isn't eating, either. I also noticed that he's opening and closing his mouth a lot.

I noticed yesterday that he had a bit of white fungus on his gills, which cleared up today. I'm assuming it came from his gross water before the change, and got better because of the clean water, so I'm not too worried about that.

This all may be due to stress, but neither his gills or tail are curled forward.

I apologize if this is all normal behavior, I'm just concerned because he's not acting like his usual, perky self at all. He won't eat, he's contently hiding, he's just acting very solemn and under the weather. His gills are very pale from lack of movement, too.

Someone, please help me! I already lost one axolotl, I don't want to go through that again. My little guy means the world to me, and I need to know if there's something wrong with him and if there's anything I can do to help him feel better.

Sorry for all the info, I appreciate anyone taking the time to read. Thank you!

Do you have any pictures and the tank parameters? And what are you feeding it?

I keep him in a 10 gallon tank, and generally only feed him bloodworms. (He's still pretty small, so I don't want to feed him night crawlers or anything like that quite yet.) It's a bit hard for me to get a picture at the moment because he's always hiding.

UPDATE: (because I can't figure out how to edit posts)
I checked up on the little guy this morning and he seems a but better! More of his fungus has cleared up, and he's eaten the bloodworms that I left out for him! He also seems a little bit higher energy and is moving away from his filter and fan.

UPDATE: he has made a full recovery I've come to the conclusion that he was just a bit sick due to the disgusting condition of the water before.