I don't see any bugs and the leaves are not spotted, but my zucchinis and cucumbers are not producing. They have flowers and when the flowers fall off, the fruit starts and then it turns yellow and dies. Some do not even produce the fruit at all. Please help.
Zucchinis and Cucumbers Not Producing
Certified GKH Gardening Expert
The white coating on the leaves may be powdery mildew. The darkening vines and deformed fruit indicate a virus. I'd remove the infected plants. As for your tomatoes, some yellowing of lower leaves is typical and nothing to worry about.