I put my endi from a 10 gallon quarinte that he was in for 2 weeks into a 120 to grow up a bit, over night I noticed he was getting some fin rot so I put a dose of melifix in the tank, the next day it was horrible and I moved it back to the 10 gallon and it has only gotten much worse. He does not wiggle his tail anymore it's like the back half of his body is dead any treatments would be great because I am clueless on what to do.

