Answer: What you describe sounds like powdery mildew, a fungal disease that attacks plants when nights are cold and daytime weather is warm. You can try a fungicide to control the problem but usually once it attacks plants it's hard to control. Pruning might remove the damage and open your plants up to better air circulation. If you choose to use a fungicide be sure it is safe to use on the affected plants. Good luck with your garden.
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