I would guess too much rain, with all the water running off the roof. You are getting a lot of dirt and stuff hitting the leaves during all the heavy rain storms .

The problem plant is it next to the downspout?

David, believe it or not, those look like some fairly healthy leaves and I would probably have left them on the plant. There is no yellowing around the holes, just brown dead tissue which makes it look like the plant has walled off the damage from insect chewing. If that's the case, you are darn lucky because there are so many squash problems that are transmitting by insects. Your leaves otherwise look very clean and green. No fuzz, no yellowing halos around the holes, no darker green spotting, no lumpy leaves, no wilt. No eggs or egg cases, no insect nymphs.

The insects that bother squash are usually not hard to spot, although the silly bug that is called "squash bug" will quickly run to the opposite surface of the leaf when you try to look at it or remove it. Green spotted and striped cucumber beetles will bother summer squash, too. All three of theses are super common around here and spread diseases.

Have you lifted every single leaf to look at the undersides? Insects on squash often hang out on the underside. Fruits are often affected by the same insects (and microbial diseases) that affect leaves. The fruit you picked looks good, especially if it is a yellow crookneck, an old variety with slightly bumpy skin.

As long as you are inspecting your squash be sure to check the stems for holes and splits which could indicate the entry of squash borers. You might find frass (looks like saw dust) on the ground or stuck to the stem where a borer has gotten in. That wouldn't be what the damage is on you plant right now, but it is just good to catch borers ASAP because they can wipe out you vines pretty quick.