This is a link to diagnostic keys from cornell. Cucurbits have fuzzy large leaves and those leaves probably evolved in a relatively dry climate to capture as much water as possible.
In wetter climates that adaptation can lead to more bacterial, and fungal diseases.
https://vegetablemdonline.ppath.cornell. ... afKey.html
Plant high on mounds and cover the ground where the leaves sprawl with weedblock and mulch with straw to keep the leaves and vines off the ground as much as possible. You can trellis some squash and use panty hose or mesh bags to support the fruit. You need a strong trellis to carry the weight. Water only where the vines are planted and try to keep the leaves dry. Drip systems are good for that. When the weather is wet or humid, begin a preventive anti fungal spray program. It is easier to prevent than try to cure fungal problems. chlorothalanil and mancozeb are a good preventive combination. For powdery mildew copper sulfate can be enough if it is used early and it is easier to find.
https://www.ct.gov/caes/lib/caes/pdio/di ... icides.pdf
Remove, bag and trash diseased leaves, don't let the spores multiply or leave the leaves on the ground.
Happy gardening in Hawaii. Gardens are where people grow.