Hello, I am a fairly new gardener. I've planted cucumbers for the first time this year, and for the first month, they were doing very well. Suddenly, though, they are fairly rapidly looking dreadful and I just cannot figure out what the problem is. I have not changed anything I'm doing. I can't see any visible pests, but last year I had quite a bit of trouble with spider mites, so I suppose I cannot dismiss the possibility of a pest (I didn't post in the pest forum because I cannot see any, however I apologize if I still chose the wrong forum). I don't know if I'm caring for them incorrectly, or what could be the problem. I have attached photos of the damaged leaves. The first two photos show the beginning stage, the last show their current stage. Also, strangely, my new seedlings are doing the same thing. And, my tomato plants are beginning to show similar symptoms (I have also attached a photo of one of them). If anyone has can offer any input, I would be so grateful. Thank you for reading.