What is wrong with my fish?

We just added this goldfish to our tank 5 days ago. I put her in a hospital tank yesterday because something is wrong with her. At first sight she looked fine. Her body was a little oddly shaped but she didn't look damaged. After the second day I noticed she was not very active and sort of reclusive. By day three she was on the bottom of the tank all day, basically not moving at all unless it was dinner time. Also there were black spots on her scales like they fell off or something. I was adding Mela fix to the tank daily to treat another fish I had for some minor tail rot and thought maybe it was a weird reaction to that but after doing some research i know that is not it. I learned a little about swim bladder infections so I gave her a pea today. She ate some of it then sat back on the bottom of the tank and is not moving again. I also read about fish TB and was wondering if that could be it because of her crooked body? Also read a little about jungle parasite but couldn't find much on that. Could it be that? I know that laying at the bottom of the tank usually means swim bladder but the missing scales and the body shape is what is confusing me. Please help and thank you for your advice!