Had some beautiful vines growing this year, Cukes, spaghetti squash, butternut, zucchini, etc. about mid-summer the vines started browning and dying from the center out. The peripheral vines still look healthy and are flowering, but the stuff in the center is gone. Is this vine borer or a different problem? Noticed it last year too, but only had a single pumpkin vine so didn't analyze it much.