Baby Toad is a bubble?? Weirdest thing I have ever seen!!!

[Umplumpa]

Okay. So I have raised tadpoles for a couple years now. This year I kept three, one in a 3 gallon aquarium, and 2 in a ten gallon aquarium. I would like to be clear that I have spring water, and I made sure I did my 50% water changes. In the ten gallon my 2 tadpoles turned into little toads, as expected. In my 3 gallon, the one tadpole did something so incredibly bizarre I don’t even know how to describe it. It began growing back legs, as usual. Then front legs, as usual. After it’s front legs popped out, I left for 3 days. When I came back, it was floating upside down in the water.

I left plenty of places for it leave the water, and my other toads left the water fine. So I have no idea why it wouldn’t leave the water. But I found it belly up, floating by my aquatic plants. It no longer had a tail, just a stub. I quickly took it out of the water, and set it on a wet paper towel. It’s body was completely swelled, it looked like a water ballon, it’s tiny legs could barely keep this giant baby toad upright. He appeared to be in a giant clear bubble. He kind of moves his tiny legs around. He has two tiny eyes, and a clear bubble around him. With 4 small legs. Will he survive the night? I am completely clueless on what to do? My other two toads are very happy, and eat a lot! I have attached some pics. One is of my healthy toad for comparison.