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.
Answers

Quetzel

Sounds like he ate something that didn't agree with him. Keep him quarantined with clean water and slight or dilute antibiotic. Do not feed. See if he improves.

Emiliana

Update- he's dead. Had been having several seizures day before. Woke up in the morning to find slimey bubbles in his tub. Was barely alive. Died early afternoon. I still have no idea what caused his issues and death.