Cucurbits - squashes, zukes, cukes, melons, etc. - are extremely prone to PM unless selecting a variety specifically bred to be resistant. Much of it's due to their growth habit. They lay close to the ground and produce an abundance of pretty big leaves, both of which reduce air circulation, one of the key elements of PM development, as well as tending to keep the soil area rather dry (also a factor). Trellising these types of crops can go a long way in discouraging PM but not all cucurbits respond well or are adaptable to that sort of growth.

Almost NO fungicides are curative - they are only preventative and need to be started very early in the growing season to be very effective although they will help to reduce the spread to unaffected foliage. Unfortunately, PM spores rapidly become resistant to single fungicides so best to rotate through 2 or 3 different ones to maximize effectiveness. And they all work more or less with a similar degree of efficacy - potassium bicarb, milk, neem oil, hydrogen peroxide, chlorothalonil or sulfur sprays

PM tends to infect the oldest foliage first so removal of heavily damaged basal leaves should help. As will deep watering at the root zone to prevent the soil from drying excessively.

Thanks, I have had limited success. With a lot of work I can slow it down.