sideways and upside down frog

Question
About a month ago I bought 3 fire belly toads.  After about a week one disappeared and could not have gotten out of the tank, and I assumed that the larger of the remaining two had eaten it.  Everything else was fine for about 3 more weeks but now that frog that is larger is swimming sideways and upside down and has one eye that looks like a bubble about to pop.  Could it have gotten sick from eating the other frog this much later?  Does is have an infection?  It kind of looks like the insides of his body are twisted up, and when he hangs in the water upside down his back legs hang down, as if his stomach is his back.  It's like his joints are broken and everything is pointing the wrong way.  Please help!

Answer
It sounds to me like the other escapee didn't escape but died somehow in the tank and was missed and infected the water.  I would do a water change and install a filter as well as make a trip the vet to diagnose the specific infection which is what this sounds like.  I would also take the infected toad and place it in a quarantine tank by itself so the other animal doesn't become infected as well.