Illness/Sickness: Is my axie sick?

First post on here... my axolotl of about 5-6 months has been acting a little funny the last week or so. My axolotl, Hank, gets fed a block of bloodworms nightly. I use level pH water when I change the water in the tank. His tank has a fine, black sand substrate on the bottom. He's always been a fairly active axie, and always sleeps at the bottom of the tank.

Just before he started to act funky, I had fed him a handful of ghost shrimp as means of trying to mix up his diet. He has been pooping, but maybe not as often as normal?

Issues over the last week or so have been:
-He has been much less active and interactive to people in the room.
-He doesn't react to my touch as much as normal.
-His gills don't get as bright pink as they normally do after feeding him.
-Has been floating while sleeping on occasion.
-About an hour ago, he just threw up his meal from yesterday.
-Since throwing up, his gills have become more of a purpley color than just pink and I can also visibly see some of the veins in his fin/tail. (The thin part)

So here are my questions:
1.) Do I feed him too much?
2.) What is the ideal kind of water to use?
3.) Is the issue constipation?
4.) Am I over worrying?

I've searched up lots of topics trying to find answers, but couldn't seem to find what I was looking for.

So any help would be greatly appreciated. I love my little Hank and want him to live a long, happy life. :happy:

pictures are really helpful if you can get some
how old is this axie and how large? their behavior settles with age but I'm wondering if he should be getting fed something more nutritious at this point like earthworms
also, water tests? pH tends to be the least of problems. honestly I rarely test it. What are ammonia, nitrite and nitrate levels?