Albino Clawed frog paralyzed and not eatting, please help!?

I ve been trying to find out what could be wrong but I cannot find anything online. He does not show signs of any infection or red leg. The first day, he had what seemed like a seizure. He could still use his back legs but had decided to stop eating. A couple mornings later, I found him belly up in the tank. Thought he was dead, but then I saw his front arms moving trying to push himself upright. His back legs were paralyzed. I grabbed him in the net and brought him to the surface for air. Right away I put him in a quarantine bin with water levels low so he could breathe by just lifting up his head. I ve had him like this for a few days. His back legs are shedding everyday and he still refuses to eat. He keeps having seizures now but his back legs don t move during them anymore, his hands go crazy and he jerks his head and opens up his mouth wide, it almost looks like he s screaming and it absolutely breaks my heart. Is there anything I can do?? What might be the cause? And if there s nothing I can do...how do I put him out of his misery? He was kept in a 20 gallon tank with 4 other fish (1 corykat, 3 tetra) it had a filter, was clean, and levels of everything in the water were fine.