Hello Kathy,

I am so sorry that I am responding so late to your question! 

It appears that your plants have powdery mildew. Unfortunately, there is not much you can do with these plants. From now on you can purchase powdery mildew resistant varieties and make sure to give your plants plenty of air space and room. The use of fungicides has also been found to be helpful; if applied at the correct times. Inspection of plants during the beginning of the fruiting stage is crucial for proper timing of fungicide. 

Here is a very helpful factsheet regarding powdery mildew and what you can do to help prevent it:

https://www.vegetables.cornell.edu/pest-management/disease-factsheets/cucurbit-powdery-mildew/