Answer: What you describe sounds like bacterial leaf spot. It occurs when the plants are not getting enough sunlight, the foliage remains wet for long periods of time and the air circulation is poor. I'd suggest pruning away the affected plant parts, both to remove the pathogens and to open the plants up to better air circulation. You can control the rainfall, but you can avoid overhead watering, soaking the soil rather than the entire plant when it's time to water.
Best wishes with your garden!
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