Its mildew powdery most likely. All of my squash and cucumbers eventually succumb to it, but I still can get 20 or more good cucumbers from the plants before then. Squash, cucumber, and tomatoes need to be on a regular fungicide prevention program especially where we live as the air is humid most of the time. I spray within 3 days of rain. It is not so much the rain as the humidity from all the water vapor steaming up that promotes the fungal growth. It is much easier to prevent than to cure.
It helps to get a cultivar with some resistance to the diseases. I have grown Diva, Tasty green, General Lee, and Suyo. While not totally resistant, the vines live long enough to produce good fruit.
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Happy gardening in Hawaii. Gardens are where people grow.