Okay, I think at this point it'd be good to look at what isn't right, since clearly something is not good,
and what changed. Many have chimed in to try and give you their thoughts of what looked like needed
correcting. The part that changed were the new fish, so maybe the water is good and the new fish brought
in parasites and/or disease. Karl listed Proform-C and Praziquantel (often refereed to as Prazi, Fluke-M is
another option that works well) that will control most of the different parasites. I'd get both of those as they
are good to have on hand either way.
Bacterial infections are sometimes more challenging to treat but Mary suggested Crystal Clear Wipeout
which sounds similar to the Kanaplex you're considering. At some point YOU are going to have to make the
decision on which way to proceed as all we can do is suggest methods of treatment. The local club contact
could be another great pair of eyes and being there in person might be able to offer you another valid option.