First thing I use when I have this sort of problem is a copper based spray. You should be able to find several different kinds at anywhere with a garden center.

Fungicide is a preventative not a cure. I would isolate any plants that dont have it and treat them. Once a plant is hit like that I dont see it being cured.
You could try but dont expect any positive results.

Unfortunately, I agree with both Edymnion and Dave. Copper based fungicides/bactericides seem to work better than "organic" ones. But, some common organic ones are neem oil, serenade, potassium bicarbonate.

On the flipside, dave's right. It's best to treat for these things BEFORE you see the symptoms. Kind of hard to do if you don't know it's there and can only be figured out from the same symptoms occurring year after year or taking a plant to a lab/university and having them test for whatever microbe it is. However, I have read of people successfully eradicating/minimizing the disease to still get successful grows and harvests. As dave mentioned, isolation is prudent, if possible..

Can you remove some of the most affected foliage without stripping the plants too much? Like in the pic, maybe those two largest leaves, then treat.

Are you watering overhead? If so, stop that!

As with all soil borne pathogens, rain splashing is a major cause. A layer of mulch might help.

Good luck.

Kevin

P.S. Post the pics in the Garden clinic forum -- they might have better info.