I'm actually signing up on this site because I have a problem. In the picture below is one of my froggies. This one is deceased along with all of it's siblings excluding one (and the tadpoles I released when the eggs hatched)

My problem is that whenever they start to go through the evolution, they suddenly die. It usually happens around halfway through the "tail dissolving" process. The last time I had tadpoles their tail didn't dissolve until after they started breathing air. But these ones never start to breathe air. I have put various sticks and other floating object for them to climb on in the cage but it never happens.

Because they haven't finished their evolution I'm not sure what kind they are. I found them in Northern Maine after the snow melted in a ditch. Does anyone have any idea what might be wrong and how I can save the last one?