Also in the bunch is a photo of one tomato plant (a Green Zebra) that never did much, and then just wilted and started to die. It didn't get the yellow spots, but fared the worst of all of them.

I'm not sure it's the same thing, but other plants in my garden are showing similar signs as these yellow spots. The last photo in the folder shows Sweet Pea leaves and how they're looking distressed.

Anyone know what's causing this stuff, whether I should be concerned, and if so, what I can do about it?

So Google pics (GoogleImages) of both possibilities to compare to your plants. Different treatments for both.

Hope this helps some.

Dave

I Googled "Gray Leaf Spot," but it looks different to my eye. My issue is yellow spotting, while the Gray Leaf Spot seems to result in small, circular, brown spots.

I'll take a look at the undersides of the leaves when I get home. I remember seeing, in previous seasons, signs of webbing among some of the marigolds I plant around my tomatoes as deterrent to the Tomato Hornworm.

I will say that the sweet pea damage I posted does look very different than what I'm seeing on my tomatoes, so I probably shouldn't confuse the two in the same question.

Thanks.

-Ray