Hi everyone! We've got something cycling through our tank and we don't know what it is! The fish will be acting fine and eating great. Then, suddenly they will seem off but still feisty and eating. I've attached a photo of what they look like. This fish in the photo was still super feisty, eating , and seemed fine other than looking like this. Within 24-48 Hours, they will be dead. I've tried treating with Melafix and Pimafix but neither seems to be helping. I have lost 3 Africans and 1 pleco to this. I prefer to reserve the bigger drugs for when it's really needed and I have no idea what to even choose. I've been ensuring my water parameters are great and this tank has been established without any problems for 2 years. Help! TIA.