Answer: If entire leaves are turning white it is a response to cold nighttime temperatures. Usually the lower leaves are the ones that turn white and the upper leaves are just fine. However, if the leaves have a white coating on them, it could be powdery mildew, a fungal infections. The affected leaves will eventually turn brown and dry up if this is the case. Aside from pinching off the affected leaves, it is difficult to stop the spread of the disease. I hope it's not powdery mildew!
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