Paragard doesn't have a really good track record with marine fish IMO. It used to work pretty well a number of years ago, but I wonder if they changed the formulation? It is a mix of aldehyde and malachite green. Since Seachem says not to use it with Cupramine, using it with copper power or coppersafe would also be contraindicated.
A proper copper treatment, using a good test kit (Hanna checker for example) will handle marine protozoan diseases by itself, so no need to dose these at the same time.