Yup, with the proteinaceous diet most frogs need (frozen bloodworms, for example, are a favorite), pollution issues can be a common problem, unfortunately.. that might have been what happened with yours, Mavis <img src="/images/graemlins/frown.gif" alt="" /> .
A thing on clawed frogs (abbreviated ACF), they are not only different from African Dwarf frogs (ADF) in size. They are also more predatory, and will actively hunt smaller fish, so just watch out for that if you keep fish like tetras, barbs, livebearers. ADF's tend to make better community tankmates (not really a big deal for Dina, since she keeps her ACF with large fish anyway). Ammonia will be a problem with goldfish regardless... they are messy fish that need lots of room and filtration.
And yes, meds can always be a tricky issue, even in a fish-only tank; one of the reasons why I try not to get to the point where it becomes necessary. Dina, I suspect that the one you were talking about with the metal ions was copper...this is a common ingredient in many anti-ich treatments (not only a little touch-and-go with frogs, but instant death for all invertebrates).
Here are the links to those two sites I was talking about earlier, for all those aquatic froggy fans out there:FrogLand African Dwarf Frog by David Cecere