Lots of things can cause squash leaves to yellow. Usually it means my squash plant is succumbing to squash vine borers or powdery mildew. Did this come on suddenly? Do you have some pictures?
The second and third pictures down on this page
https://www.peakprosperity.com/wsidblog/86005/how-control-squash-vine-borer are really good images of the kind of damage you'd see on the vine close to the yellowing leaves if they're the culprit.
Yellowing from powdery mildew is preceded by the powdery appearance of the leaves. It's pretty distinctive.
Outside of these two things which I have so much
experience of, there are other pests and diseases.
In the case of a nitrogen deficiency, what I've seen in other plants is that the yellowing comes on gradually. How quickly have these leaves changed color?
edit: their/they're