I can't figure out what's wrong with my plants. They're all in containers except for one but all have this wilting, dying leaf thing. It visually resembles the pictures of powdery mildew because it starts with the tiny yellow spots that turn into totally yellow, then brown and dead, but I don't seen any gray powder on the surface of the leaf. I'm scared it's Verticillium wilt since all my plants have it (grown from seeds last year), including the one plant I bought new this year. That would seem to indicate something from the soil/environment that carried over and infected the new plant. What is it and what can I do?

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