Squash fruits are ending up rotten.

I have an extremely vigorously growing garden this year and the squash plants are going nuts. Dozens of flowers, massive leaves, lots of squash fruits.

Yesterday and today, Ive noticed a good number have begun to rot. Some start right before time to pick, some rot extremely young.

I found a slug on one of them, but the majority just seem to be rotting by their own volition.

Am I watering too late some times? Watering too much? Anyone have advice?