Because your other frog has died this has definitely got to do with water quality or feeding. What do you feed your frogs and how often? What size tank and what filtration do you use? Do you have a water testing kit? Do you use a water conditioner?

Without the answers to these questions we can't begin to guess at what is wrong with your frog. I would recommend putting him in a smaller container with only 3-4 inches of water. If you have Stress Coat water conditioner you should add some of that. The shedding is from stress probably caused by the water conditions.