The reason siva said that it could have side effects (organ damage) is because freshwater fish are not adapted to live in a brackish environment. That is just what I think her logic might be.
Now with mixing those meds, it could be dangerous, and I don't recommend medications unless your fish is suffering from a extremely severe illness. This is because it can also create resistant strains of bacteria which makes life harder on you in the long run.
If I were you I would finish up this run of meds, and then see how he does. Just keep his water pristine throughout the process.
><(((º> Aaron ><(((º>