Newt suddenly stopped eating and staying on land

I have two Chinese firebellies. The younger one which was super healthy suddenly stopped eating and is on land and refuses to go in the water or eat. It's been almost two weeks of no eating or in the water. I changed the water thinking that was it and even put the newt in shallow water to hydrate and see if it helped, because I saw air bubbles trapped thinking it was on dry land perhaps it's shed skin is stuck.

Nothing came off and as soon as the tank was cleaned and the newt put back it refused to go in the water like normal.

My other newt is doing great and shows no problems so that should eliminate housing issues.

I'm not sure what to do now that my newt isn't eating, it was plump before with a great appetite now it's wasting away.

What is the temperature in your tank? The newt may be out of the water because the water is too warm. The smaller one might be more sensitive to warmer temperatures. It might also be on land and refusing to eat because of illness, or because the other newt is being territorial. Check out the link to the Caudata Culture website below, there is a ton of information on there.

Caudata Culture - Frequently Asked Questions

It could be temperature, it could also be other issues with their set up. Has anything else changed you can think of in the period leading up to you noticing the problem?
I would say start at the beginning and go through the whole set up eliminating things that could be upsetting it. Check the water temp and quality first in case the water change has upset the cycle and go from there. Depending on how the tank is set up you could try adding some live plants if there aren't any at the moment, plants are a good way to encourage terrestrial firebellies into the water.
If you could post some pics of the tank, it might be easier to offer advice on what's wrong, the kind of behaviour you describe is more common in stressed, newly purchased newts, not settled ones that are used to captivity.

I tried putting the newt in a seperate hospital tank with shallow water to rule out aggression, water issues, etc. this is what I did when I first got the newt when it was in poor condition and it had done great.

But so far it still refuses to go in the water or eat? Nothing I'm doing is working.

There could be something that happened only thing out of the ordinary. We had a leak from our shower and soapy water leaked into the tank, I did a full cleaning of the tank. My other newt is fine from the ordeal so I'm guessing this isn't the issue, unless this one absorbed more soap. That's why I've been doing frequent cleanings and soaking the newt in clean treated water but perhaps this isn't the issue.

The newt eats earthworms, could a parasite be an issue? No idea why it would only bother one newt but a possibility.