I'm trying to clarify things to get an idea of what is going on. A lot of us have multiple bulbs/lamps/heaters etc on the tank so I was just clarifying that I was reading correctly, that there was only one bulb and it was only on for 12 hours. What is the night time temps when it is off? Big temp swings could contribute to issues.
If you would like to send me a picture so that I can try to post it for you, feel free to pm me and I will give you my email address.
As for the fatty diet, yes the diet has been fatty. Mealworms are fatty and you said that is the main food source. (I did read that you will be changing it up, but that's what it says.) Waxworms are fatty, super worms are fatty, pinkie mice are very fatty. When you wrote that no feeders were being used as treats, I assumed all of these were regular foods other than the mice that you specified were occasional. Primary food source should be roaches, crickets, or night crawlers (can get them at walmart, make sure they are night crawlers and not earthworms.) I'm thinking there might be an obesity issue, we've seen it here before, but without a picture I can't assume that.
I'm sorry your frog isn't feeling well, hopefully we can get this figured out.