I have 4 largish?? Southern Longear Sunfish in a 55 gallon tank. A few weeks ago I left on vacation and ended up leaving them on their own for 14 days. This is when I first noticed problems. The room they were in was really warm and so was the water temperature. I keep these with some goldfish (all fish have been together since Sept 2018). As soon as I came back I noticed that some of the goldfish were missing scales and some of the Sunfish seemed to have peeled skin. Almost everyone recovered in the last 3 weeks. I have though noticed that 1 of my Sunfish has gotten worse in terms of peeling. I'm not even sure that that is what it is. I will attach a picture and those little white strips coming off the skin are now almost all over the body. I see the fish is mostly acting normally but it will violently shake often and scratch/rub itself on a rock. I've been keeping the tank at around 70 degrees for the last 3 weeks with the use of AC in the room that it is in.
My question is, could this be a parasite? If so, why present itself now? I have not added anything at all to the tank since I put the fish in excepts some oak leaves, the branches they were attached to and a few sweetgum fruit many months ago. All were steamed using a water bath for more than 30 minutes before adding to the tank. The leaves and tannins are now gone, should I reintroduce them?