Your soil may be infested with nematodes that eat roots or  voles, moles or just poor fertility. If you see knobby bumps on the squash roots suspect nematodes. You should try rotating your crops to starve out the nematodes.  If you send a photo of the roots I may be better  at making a diagnosis. A cold winter could solve your problem and tilling the soil a bit to expose it to the winter weather can also help in some cases. Keep growing, Marianne Binetti