Cumbers are wilting

Any ideas what is happening here?
Since taking this photo I've removed the affected bits, but ilI don't think that's fixed the problem.

That web makes me suspicious of some kind of pest, maybe spider mites?

Have you tried a soapy water spray?

I agree with Anne. At the very least, pull off all the recurring web tents, and stomp on the bugs creeping through them. I haven't seen that on my squash, but when my valued trees get something like this, I cut off all those leaves in my reach, and squish it all under my soles.