always the favorite

How come if you loose a fish or one gets sick, its always your favorite? This past week, I've been trying to nurse my favorite shushui back to health. I have always had trouble keeping shushui. Not sure why, perhaps its because they are scaleless or perhaps they are just a weak breed?? Whatever the reason, I purchased 3 new ones this year. They're not the first I've had. I've owned several and have never been successful at keeping them alive. I figured if I bought 3 of them that are a little bigger, maybe my chances would increase. Well, of the 3, my favorite one has developed an ulcer this past week. Harry noticed a "red spot" on him last Saturday. We were hosting the Northern Iowa Pond and Koi Club that evening for dinner. So, we just left him for Sunday. He's in my smaller upper pond where I have several lilies. That pond of fish has always been spooked. They constantly hide under the lilies, so the fact that we even saw the sore is lucky. Good thing Harry noticed it. So, Sunday we pulled him out to get a closer look and sure enough, he had a raised sore on his side about the size of a silver dollar. Dang it, dang it, dang it!!!! These fish were all treated for parasites earlier in the season, so what's causing this? Of the 3 shushui I bought, he is the one with the nicest zipper. (That row of black scales that run down their back) So, now he's in my basement. I liked this fish so much that I even went to the vet to get some antibiotics. 5 injections of Baytril. I've moved him to the basement where he's in a very small tank of water with an bacterial water conditioner and salt in it. He's not happy, I cleaned the wound and have given him 3 injections to date, unfortunately he's not looking any better. If anything its still growing and getting worse. Looks awful, and the fish looks terribly depressed to be in such a small tank without his buddies. I'm worried for him. Am hoping the antibiotics will kick in soon. If not, I'll be deferring to the vet again for help. Shushui, maybe I'm just not meant to have one????