I'm sorry to hear that...about a week ago my Red Eyed Tree frog was found dead...I loved that little guy, his name was Dorian. I live on a college campus and I normally keep a bottle of fresh water to refill his water dish daily, but when I wasn't home his water bottle got switched with one that someone replaced with vodka and I ended up filling his dish with it...the next day I found him completely dehydrated and dead...his tank mate, a tiger leg monkey frog was almost dead too, I immediately held his little body in fresh water and after a while he got hydrated again and he's back to normal now...sad times...How was your' tank set up? were there any loud appliances near the tank? sometimes if the tank is near a fridge or someone that vibrates throughout the day they can become stressed and stop eating from stress..also if they don't have proper humidity and regular lighting schedules it can stress them too.