Hi David,
Online diagnosis are not the best way to treat an sick or injured animals. You mentioned you have a fungus problem, is this a primary fungal infection or a secondary fungal infection due to injury, bacterial infection, or viral infection? There is a different treatment method required for each of these situations. As you mentioned you tried several otc medications that were made for fish and were unable to resolve the situation (which can often be the case due to drug resistance or improper dosing and/or lack of absorbtion). Jen gave you the best information available based on the information available.
In your place I would be contacting the person I got those newts from and either look to return them or get some kind of credit for them. If they will not help you out with the situation I would then look up the ARAV website to see if there are any Vets near me who treat amphibians and can help you through the use of diagnosis and the use of currently accepted effective drugs.
I'm not trying to be rude but this is really what you need to do.
Ed