1 gallon water, 1/4 cup dry milk, fat pinch of epsom salt. My tomatoes love this. It won't kill the fungus, but it feeds calcium and helps the roots uptake potassium? from cold wet soil. Greens up everything you spray it on, within a few days you'll be amazed.
I forget who posted it here first, but they deserve the credit.

on plants that are prone to fungus problems. If you start this early in the growing season, and continue it throughout, it does keep the problems at a manageable level. The plants seem able to cope with fungus better.

You say you aren't interested in non-organics, but just know that even if you decided to use them now, it is too late for them to work either....just so you are not tempted.

I won't be tempted but will keep in mind using the milk spray starting early next year. That is an issue I am now worried about...it is all over my yard now. Maybe it will be dormant next year if it is not so rainy...but maybe not. Think I'll designate one garden sprayer as my milk spray bottle. And, as stated above...might just green things up a bit as well with the extra calcium.

a favorite of mine last year, loaded with crap as you describe. Sprayed with Neem for aphids, and haven't done much else. Do water + feed them, and harvest. As not a real gardener, I have no advice. Sorry

But you have to use it very early in the spring as a preventative. It's too late now. My tomatoes are just starting to show signs of blight on the lower leaves.

Everything else still looks ok. The pumpkins usually get powdery mildew on the leaves, but they are in a partly shady location.