The tiny yellow spots 0- are they your concern? If so, very out of focus but,even so, I'd guess aphids. If so, not responsible for the leaf damage.
As for the leaf image, environmental. I see you're growing hydroponic system, right?
Yes Jean. I actually have found that there are a few thrips here and there, particularly on the blooms. They don't seem large enough in number to produce these manifestations though. The other orange critters (sorry I couldn't get a better zoom with my iPhone) aren't actually critters. They are eggs! Or at least they appear to be. I scraped a few off and they were very hard, almost like a hardened sap? What really concerns me about them is they are found on that surface split of the stem, which I had never noticed before until of recent.
UPDATE: A few of the lower leaves, even the new branches, are beginning to wilt and the tips are turning grey/dark blue and crumpling up. What could this be?
Any signs of cucumber beetles? A few days ago I noticed similar stem splits along with yellowing and no flowering taking place anymore. My leaf damage also looks similar but not quite as bad.
Since then I've noticed increasing numbers (kill maybe 12-15 per day) of striped cucumber beetles, mainly out at night, and have had to trim two of my three plants back in hopes of saving them from bacterial wilt.
Here is a link that might be useful: my cucumber troubles