why are the squash plants’ leaves curling
I have summer squash in large container. Some are doing well but the leaves of two plants started curling and they stopped thriving. The same thing has happened with a butternut squash in the ground.
You may be seeing squash wilt: https://www.gardeningknowhow.com/edible/vegetables/squash/signs-and-treatments-of-squash-wilt.htm
or the effects of an insect such as thrips or aphids. You can take some leaf samples to the Extension Service for analysis; this link will help you find one: https://www.gardeningknowhow.com/extension-search/
but in the meantime, you might try a simple home remedy such as neem oil to control whatever bug is molesting your squash: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm