I'm having a tough time with my squash this year. Zucchini is thriving but the butternut and spaghetti vines are growing then the leaves die. I get lots of flowers and the vine keeps growing but the leaves shrivel up and the stem is soggy and I have no squash. Am I under watering? I think I'm running out of time to get any squash this year and it's really disappointing. Any ideas?