That is your problem. Mealworms have an exoskeleton made of chitin, which is what your fingernails are made of. Chitin is very hard for a frog to digest and break down. Continuous feedings of meal worms can and most likely will cause an impaction. Crickets should be the main diet. Meal worms should only be offered as treats or not at all. This means 1 or 2 meal worms a month. Try something more nutritious like silk worms or horn worms.

The warm bath that Paul suggested probably saved your frogs life.