Good lord! 15 plants? Do you sell them somewhere? I have 1 zuk and 1 yellow squash and I'm already looking forward to August 8th "Leave a zucchini on your neighbor's porch day!"

I have noticed that one of my plants got accidentally semi uprooted. Where the vines were touching the ground, I got some new growth.

I'm in CA where we don't get the borer or squash bugs.

They're doing fantastic, but you're battling powdery mildew, squash bugs, cuc beetles and maybe borers? Not clear what squash we're talking about or where you are. If this is zucchini, sure, just trim off old growth. Those trimmed ends will dry quickly, and be no more open to pests than the rest of the plant. If you have borers, they'll let you know pretty soon that they're there, by killing off large parts of the plant.

Best way to deal with powdery mildew going forward, besides ensuring really good air circulation, is to plant resistant varieties. After getting my winter squash pretty much wiped out two years ago, I make it a point to choose only resistant varieties -- has made a big difference (as has keeping up with the weeding to help with the air flow around the plants).