Please help

I messed up. Saturday I did a big water change in my goldfish tank and disrupted quite a bit of the gravel trying to clean it up. I guess it was too much for my comet and he deteriorated over the past few days. He was hiding and wouldn’t come out. When I moved the cover of his hideaway he was being constantly swept away by the filter current. He got sucked to the filter twice. I did a small water change in order to introduce aquarium salt. However his tail looks fluffy and frayed and cottony. I thought it was fungal but now I am not sure. I introduced artemiss microbe lift. I’ve done two doses one today and one yesterday. I was curious if anyone has any suggestions as to what I’m dealing with and if I can save him. I isolated him to a container I hooked to the side with holes in it to allow for protection from the filter.