Looks like powdery mildew. A group of fungi that get on a lot of houseplants and vegetables like squash.
You can try one tablespoon baking soda and one-half teaspoon of liquid, non-detergent soap with one gallon of water, and spray the mixture liberally on the plants morning and evening.
It’s either powdery or evidence of thrips. Most Likely to be powdery mildew. The formula that bowl brow suggested works, and I’d also add one half teaspoon of hydrogen peroxide as well to ensure all the bad bacteria on the plant is being killed off