I had to trees do the same thing, my cherry and pear trees. I really think it was too much heat for too long and possibly a fungus. you can't do much for the squash plants but the trees can be covered with a old sheet if they have leaves when it starts to freeze and once they loose the leaves then brought indoors to a non heated garage/shed if they are in pots. this will help them weather the winter. they are doing this sudden leaf thing because they didn't get enough stored up for winter to survive. plus the wackey weather doesn't help any.