I noticed that you feed your frog crickets and worms. I have seen instances where frogs have had their mouths damaged by eating live vertebrae (mice and such). The way that pac man kill their prey leads them venerable to bites from the prey and sometimes the prey can bite the inside and outside of the mouth because it is obviously being threatened being swallowed whole by the frog. Their mouth can also be damaged when lunging at prey and striking fixed objects like rocks or unsafe feeding tongs. These injury's can lead to mouth rot, see link http://www.peteducation.com/article....+1796&aid=2385 . I hope this isn't the case but might want to read this just in case. I know the link mentions snakes and reptiles but I know that pac man frogs can get mouth rot. I hope your little dude gets better soon