Fungicides generally do not work that way. You need to pair the fungicide specifically with the disease it is intended to control. Some do target a broader range of organisms than others but you still need to confirm they will be effective for your needs.

What fungal diseases on what plants are you concerned about?

btw, many 'organic' or natural fungicides are very effective.

That's exactly right. Fungicides target specific diseases, and they do so because their mode of action is different. See https://www.frac.info and click on the FRAC code list. If you're going to use multiple fungicides, do yourself a favor and choose ones that have different modes of action. I use chlorothalonil (M) and tebuconazole (G) alternately, but even that doesn't fix everything. Note also that "systemic" fungicides are actually absorbed by the plant locally so, to some extent, they can "cure" an infection. Everything else is just a preventative. Chlorothalonil (Daconil) is often recommended as the best all-around tomato fungicide, but it isn't systemic.

I figured that was what I was going to hear - in the past I always got a very specific answer and it never covered another issue. THANKS!!!