Cucumber pests?

My cucumber plants started looking a bit bad about a week ago, with more and more spots showing up. Now one of the leaves has died entirely, but I didn't find anything conclusive about what it might be (other than cucumber beetles, which sounded like there's nothing to do about them except prevent them from getting there in the first place!).

This is my first summer really gardening. Does anyone know what this is?

Looking at your leaves, there's something else going on and I think it's a nutrient deficiency. Just like humans, if a plant has a weakened immune system,  it's more prone to disease.  Check out a nutrient deficiency chart such as this:

https://goo.gl/images/BQLjEZ