Adding ..I am located in South Texas .

The damage on the first several plants is minor. But look now and then to determine if the damage is getting worse.

If not, could be that the critter(s) is(are) gone. If increasing, check the tops & backs of the leaves as you search for the hungry beasts.

The cuke is definitely in trouble. Perhaps short of water at the roots and/or reflected heat off the fence/wall?

Is it in a pot? If so, what size?

How often do you water?

And how? (drip, trickle, ooze, hose, or sprinkler?)