So do you think all this acidity has something to do with the question you asked previously about why you have so much trouble with fungus on everything?
Don't we usually say more fungal soils are more acid and vice versa?
I found this:
The pH or acidity of the mulch is another important factor. Sour mulches that give off acrid odors may range in pH from as low as 2.5 up to 4.8. Highly acidic mulches are toxic to most plants and promote the growth of fungi. Bacteria that inhibit fungal growth cannot colonize mulches when the pH is lower than 5.2. The low pH and fungal problems are avoided if the raw material is nitrified and composted as described earlier.
It was about mulch, but seems like it would apply more generally.. more acid conditions promote the growth of fungi and inhibit the growth of bacteria that would prevent the fungi.
Wow!! We may have just figured out your problem.
It makes sense in the fact that sodium bicarbonate (baking soda) and potassium bicarbonate solutions are treatments for plant fungal diseases.
So if you raise the pH of your soil AND of the water and you treat your fungal diseases with baking soda solution, everything should get better including all the disease problems!
As long as your water is so acid, I would be extra careful about never watering leaves, only the soil, so as not to create environments on the leaves conducive to fungi.
If you let your water sit over night will some of the acidity dissipate? I'm thinking of how chlorine and fluorine outgas from water that sits. But I don't know what is causing your acidity. You might give it a try though... you can just get litmus paper strips to test it.