I agree with Mr. Corlett. It is probably painted plywood. While everyone seems to think it's wonderful stuff, it splits, swells and shrinks. People are willing to pay a premium for this opportunity. If you want a solid, stable surface for painted cabinets high quality particleboard and MDF are superior to plywood. I've had too many custom cabinet maker's tell me this through a number of renovations. I got the message. Sorry.

Yep, it was hail! Fortunately they seen to be recovering well. Question: it is supposed to rain all next week. It is sunny and dry this weekend. Should I stretch the time between watering my plants (zucchini, tomatoes, cucumbers, peppers in containers, pole beans in the ground) in anticipation of a week of rain? And it's considerably cold right now than it typically is this time of year. At what point should I try to bring them in overnight?

Frankly, it looks like mechanical damage. Have you got a cat or some domestic bird, like parrot?

It is possible you have Early Blight. Mine do the same thing. They will be fine until the first full day of high heat and humidity then it just explodes. The first thing to do is get all the bottom leaves trimmed off - I've read that it is fine to take everything off at least the first foot of your plants and even up to 18". Get them in the trash then wash your shears and gloves with bleach. This will help stop the spread. Copper fungicide or Daconil sprays, or Epsom Salt drenches are usual recommendations. I usually start spraying mine about 2 weeks after planting. Good luck with yours.