I have a Platy that Ive had for about 2 years now

I recently moved and had to reset up the tank

Im no Aquarium GURU but I did reuse most of the water that was orginally in the tank before i moved the tank


Well approx 3 weeks after I moved My Last Platy who seemed to live though everything in the past Got some weird sickness

Hes Bent in half practically and Is swimming upside Down
But he is still swimming and eating


Any reccomendations?
Im a lil sentimental towards this fish cause He Is one of the first ones I ever had