If it's not, then you could try some MILD (not agreesive) treatment to match what a municipal system would have.

Putting too much in, aside from heath issues will negatively affect your heater and other components of your system (rubber, fittings, fawcets, etc.). A little is probably fine. If you can smell it when you drink (unless you're hyper sensitive) is probably a good measure of what's okay. It should match what you'd smell (or not) in a municipal water system.

Periodic flushing is probably the way to go, after you get rid of the smell. If it's gone from flushing, then I'd keep flushing it more often. If it's only in the Hot Water, then empty-out the hot water tank. IT COULD BE IN THE HOT WATER HOSES, and not just the heater.