Well Jack; this is certainly a perplexing event. Agree with Colleen/Jerrod and only way to know is conducting a necropsy. Have heard of "Sudden Death Syndrome" but that dry bath dish is still a mystery.

By any chance; have anything different happened in the frogs room last few days? Think in terms of deodorizers, carpet cleaners, painting; anything that involves chemicals or fumes. Also, check your dechlorinator to make sure it's dates are good.