Answer: How disappointing for you! It sounds like you are doing all the right things. Tomato plants can fall victim to many fungal diseases and black, light brown or rusty spots on leaves are symptomatic of nearly all of them. Bacterial spot thrives in damp, rainy conditions and affects both the fruit and the leaves. Early blight produces brown spots with outer yellow circles. Fusarium wilt generally causes leaves to yellow and occurs when temperatures are high. Late blight hits older leaves first and rapidly progresses up the entire plant. Septoria leaf spot (or blight) begins with water-soaked spots on leaves which eventually turn gray in the middle. None of these diseases is easily controlled. You can try picking off the infected leaves and fruits, but doing so could result in sunscald of the remaining fruit. It's difficult to recommend any other control measure until we know for sure which disease your tomatoes have developed. For positive identification and treatment recommendations you can collect samples of the affected leaves and take them to your local cooperative extension office, Master Gardener clinic, or well staffed nursery for help. Once you know what you are dealing with, you can control the problem. Good luck with your garden!
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