Hi, I had 4 fancy goldfish, 1 pleco & 1 chinese algae eater (tiny thing) as of Monday in a 28 gallon bow tank. Yesterday 1 goldfish died and I noticed a white border all around it as well as on its body. The other 3 looked normal as did the pleco and the little guy. I treated the tank with Maracyn 2, which is all I had in the house. The first dose last night along with a partial water change. Water tested, all within normal range. Today another goldfish has the same look - white border and all over its body (see the pics, sorry about the quality, took with cell phone). He is still alive in the tank but swimming horribly, looking like he's on his way out. I went to check on him and found the pleco dead. WTH is going on in this tank? Should I continue treatment or do a 100% water change and clean/disinfect the entire contents of the tank? Also, can anyone identify what this is and how it got into the tank? No one new has been added to this tank, it's been established for a year and a half. Any help is greatly appreciated! Thanks!