Is it possible the spray had any of the following ingredients?

liquid seaweed or kelp
milk
baking soda
shampoo or dish soap

You could spray 1, 2, or 4 any time of the year as a sort of preventative. I would not spray baking soda unless it was a last ditch attempt to save a rare plant. It's just a little harsher on the microbes that live on the plant.

it might have had dish sop or horticultorual oil. It's the ration of the ingredients to water that is the problem. Thanks for the ideas.

Two mixtures I have found useful in controlling plant fungi are either 1 teaspoon of Baking Soda mixed in 1 quart of water and sprayed every 5 to 7 days or a 50/50 mixture of fat free milk and water sprayed on the same schedule for infected plants.
Of course the best thing to do is look at the growing conditions and determine why these plants are getting this fungal infection and correct the conditions that lead to this, so you need not spray for it.