Q.Baking Soda Fungicide
I am a beginning harder; I sprayed all my plants with a baking soda, oil and dish soap solution. It appears to have harmed my broccoli, cabbage and spinach. There appeared white spots, Which I thought was residue, on the foliage. Should I be concerned? The tomato plant, which had signs of early blight, did not respond this way.
Some solutions leave residue but your picture was taken too far away from the plants and was not clear. I am not a vegetable gardener but baking soda solutions may add sodium (the harmful component of salt) and reduce B1 vitamins. I think it was once used to maintain color in some vegetables. Now it is used to combat powdery mildew (a PM alternative: you can use 40% milk + 60% water spray solution instead).