IMO:
1. A picture is worth a thousand words
2. Even though a test strip is not "old", they can still be very inaccurate. I would follow Piscine's advice and get a liquid test kit - you might be surprised.
3. As far as a blanket treatment, I would probably start with the Maracyn line -- but again, hard to diagnose w/out pics.
Question: What you believe to be the typhoid Mary fish, did it die? If so, how long after you had it did it die and what infection did it appear to succumb to?