Black Shark fungus infection, now stressed.

[itzdaviddxd]

Hello guys, I'm new to the community. I have a Black Shark (labeo chrysophekadion) and he is about 3 years old. Swims in a 40 or 50 gallon tank. Yesterday, he was upside down struggling to swim and I noticed some white spots(not ich). After research, I found it was a fungus infection and went to the pet store asap to get a treatment. I got pimafix and added the dosage required, followed the instructions on the bottle. After a couple hours, the white spots went away and he seemed fine, but very lethargic. More research and I've come to the conclusion he is stressed. He tries to swim up against the tank and is still very lethargic. I went to check on him and I scared him, made him swim around really fast around the tank and he jumped up, hit the top of the tank and went to the bottom, upside down, and shaking. I thought I lost him but I took away about 20% of water and added about 4 teaspoons of aquarium salt. He still shows signs of stress. So far this is day 4 with the pimafix. He was okay swimming and eating a little bit but not as energetic. I added my 4th dose of pimafix and again he is stressed. Do I stop since he seems to be getting better? This is a long post, sorry but I want to know what I can do to further recover him.