Well, you've mentioned two common culprits!

I'm getting the same thing on my hops, spinach and Brussels sprouts. I never see the things, but they do a lot of damage. I'm going to try to make an organic repellant out of onions, garlic, red pepper and water that someone posted a while back.

I see those same potential pests (ants, pillbugs, snails), but doubt any of those are the problem. Pillbugs don't climb that high, snails often don't either plus they leave a trail, and ants don't usually bother things except for flowers.

It's probably some other type of bug, such as a caterpillar, or larva from a beetle or fly.

Inspect at night with a flashlight, and look at the underside of the leaves both day and night.

Sowbugs can be found on the newer growth of veggies, Jim. I'm also wondering about earwigs. Our original poster is going to have to get out there and do some sleuthing.

I just figured out what the deal is in my garden-inchworms. The reason I wasn't seeing them is because they're almost the exact same color as the leaves. I don't know if they eat any of the plants you've had issues with, but it looks like i can put it to bed in over here.