I can keep the air conditioning on so that it is about 70 degrees during the day but unless someone else has another suggestion that's about all I know to do. I am sure that the pet store environment was a lot warmer that this, and that was contributing to the problem. When I first bought the newts, I could see this lighter gray shiny patch, where this sore eventually developed. But I thought it was OK since it wasn't white. I have already learned a lot.
I am now questioning my wisdom in trying to keep these creatures in Florida. In the past, I have had complete blackouts for 5 days with hurricanes. I never lost any tropical fish during those power outages, but I wonder if I would lose these newts with the high temperatures. I love them though, they are wonderful creatures.
For now, I plan to continue this treatment routine since the sore seems to be at least not as white and not spreading.
I plan to rework the terrarium since I have learned more about the proper materials to use reading the information on this forum. I have a mainly peat moss and bark base, which I understand is unsuitable, but which the pet store recommended to me. I don't want the other newt to get these sores because of my unsuitable conditions!
Both newts are eating. The one with the sore ate two earthworms and might have eaten more if I had anymore available!