i recently purchased a small porcupine puffer for my 75 gallon aquarium originally i put him in my main system since my quarantine system was taken up but then noticed little white spots and i moved him over to the quarantine system over the past couple days i noticed the top of his left fin was white and i don't know what it is, i thought it was fin rot at first but it does not look like the fin rot i have seen on my other fish in the past so could y'all please try to help me figure out what it is.