A word to the wise - do not use grass clippings in your garden beds unless you are 100% sure that they are herbicide-free. Modern herbicides are so effective and persistent, it is difficult to believe that they are legal. Because my neighbors grass has some weeds on it, I thought that their grass-clippings might be herbicide free. But they weren't.
Unfortunately, broad-leaf herbicides are definitely the norm instead of the exception to grass fertilizers these days.
Most cucumbers and melons bounce back from this kind of thing if you catch it quickly enough. I'm hoping so for my own garden. I removed as many of the grass clippings as I could and added worm castings. Now, I just pray, wait and hope.