Regardless of the situation you need to move the afflicted newt to a qt shoebox mybe even for a couple of months. I can tell you what will happen if you don;t take decisive action....death. Even if you move him he may still die but you will have been in the best position to help him. I would set up a simple box with wet paper organic no bleach paper towels. The paper towels will allow to see if fecals exist. Then just nurse him with pin crickets, mela FF and spring tails. Make sure you are dusting with suppliments that have not been opened for more than 6 months. Yes that will mean you will throw away 80% of the product. Using expired suppliments will do nothing for the health of your newt. In the enclosure I recommend adding a small water dish and pcv pipe pcs. When the newt is more active then I would switch the paper towels to a mix of coco fiber, sand, and organic soil, He may have to remain seperated for 3-4 months....It just happens that way. When I got my T marms one took a turn for the worst and I seperated him out from the rest. Now size wise he is probably only tow weeks behind instead of what looked like 4-6 weeks. In a few weeks I would feel comfortable moving him back in but why mess with the success.
I learned the hard way with a popei larvae. I hemmed and haw on the decision and ultimately he died. When I think a simple qt enclosure would have saved him. I longer repeat thse rookie mistakes.
Good luck
