Hello, when you put for temp 75f-82f for the day do you mean it fluctuates through out the day? If so you want it to stay at steady 82f, if his temps are to cold his digestive system will slow down and this could make his appetite slow down also. When you called the vet did he recommend to bring the frog in? Im wondering if the prolapse went back in wrong or as stated before maybe an infection. If he had a prolapse then that was followed by the stress the infection could have gotten worse. For a staple I would use the nightcrawlers, better then crickets health wise and they are also softer and easier to digest. And feeding these as a staple might help another prolapse from occurring being one has happened already. If he is acting off I would also change his surroundings to very quiet low traffic place. Oh and is the uth on the side of tank or underneath on the right hand side? It shouldn't be underneath, always on the side for these guys. If he doesn't eat for you soon you may have to bring your little guy for a visit to the vet for some antibiotics or something because again with the prolapse there is a good chance he could have an infection.