Alpine Newt White development on neck and chest

[Heathersimn]

I have a group of alpine newts. They were all healthy and happy. I wanted to add more to the group so I got 2 more but before I even introduced these newts I noticed their bellies had a gross white indentation on them. Looked like their flesh was degrading. I thought maybe it was some crazy contagious fungus or bacterial disease. I decided to do the sad thing and euthanize the 2 new ones so I didn’t contaminate the old group. Now months later (the original newts I have are from the same source) I have noticed one of them had the white on him. He only had it on his neck instead of neck and chest. I don’t have a photo of him right now, he runs and hides. The others in the group don’t have it. They have full orange necks and undersides,

I do have photos of the 2 I sadly put down. I’ll attach those.

Anyways the point is I don’t know what it is and why it’s there. They always have clean water, filter, plants. Happy healthy live diet. I’ll try to get a photo of the one male who had the white neck.