The winter squash problem may have been a squash vine borer. It's a moth that looks like a big wasp which lays its egg at the base of the squash and the larvae bores it's way down the vine. I've seen them on my summer squash. I've put garden insecticide on the base of the vine before they blossom and avoided them. I've seen other people dig the 'worm' out after they see leaves wilting.

I haven't had the mildew problem...yet.

The Cucurbita moshata winter squashes (butternut, cushaw squashes) have a solid stem and aren't bothered much by squash borers. I grow Seminole squash here and it is highly productive and has no insect problems. Around here, summer squash quickly gets overwelmed by borers, squash bugs, and powdery mildew and is gone by mid-July, so in the spring I also plant Cucuzzi squash (Italian edible gourd) which isn't bothered by pests and is still going strong with the first fall frost finally takes it out. Its my summer squash for the last half of summer.