Is this mildew?

Is this some type of mildew? I planted the squash from seed and now I am seeing the white spots on the plants. I thought it was because the leaves are touching the soil, but really am not sure. I have 2 squash plants next to each other and the other one only has a few leaves with the white spots, but this one looks the worst. Are there remedies that I can put together or do I need to buy something from the garden center? Can I pull them and plant something else in that spot or do I have to wait a long time? These are in a raised bed with other types of plants. Also, if the problem was caused because they touch the soil, how can I raise them up without having this be a problem, rocks, etc.? Thanks.