You are just going thru a rough patch. I had the same thing happen to me 5+ years ago. Every fish I bought was a "Typhoid Mary". However, your luck has been especially bad because you picked up fish with these odd diseases that are not easily curable.
My advice would be to stay the course for now and wait & see what happens. Believe it or not, you are learning a lot about fish diseases and treatments by having to go through this. Once this is over, I would highly recommend breaking down your QTs, sanitizing them and just starting over. To prevent whatever you've got going on from infecting future fish purchases. I would also suggest placing your QTs further apart to prevent aerosol transmission. In different rooms would be ideal.
I also think it would be a good idea to look for a different source to buy fish from. Back when I was having all my problems, my fish were coming from the same LFS or two, and the diseases I was dealing with were in their tanks permanently and just kept infecting more fish. Once I switched over to buying mostly Liveaquaria specimens, most of my disease problems went away except for every now & then. I know LA is probably not an option for you in Canada... but there must be some other online source (or a better LFS?) you can get healthy fish from? Is there a local online aquarium club in your area? They would probably know.