I have tomatoes that are not in the ground yet, and are probably potbound by now. Been a weird spring, and yesterday (May 08 2020) we went below freezing. So I can't get them out for a few more days here. They live on a wagon and go in and out of the garage. All of the affected ones are plants I bought, not the ones I propagated, and are the older ones. Mine are all much smaller.
This morning I saw white spots on the leaves. Not a lot yet. I tried warm water and a paint brush, they don't come off. I fertilized them with compost tea, hoping that will give them enough strength to hold it off till they are in the ground and have a chance.
Any suggestions? Any ID on what it is?
Try two tablespoons of any vinegar in a gallon of water. Spray the plants and the dirt around them. The tomatoes love the acid boost and most fungus and molds hate the change in the Ph. Sometimes what's needed is two tablespoons of baking soda rather than vinegar. Neither will harm the plant. Try top dressing the tomatoes with used coffee grounds for an added acid boost.