Before I sound really dumb, let me tell you this is my very first season. I have something small eating the outside of the romaine leaves and making them brown and burned looking. Also something ate an entire marygold plant and a bell pepper plant. But others are being eaten little by little...
I see ants and little red spider looking things (very little of them)

I was going to say rabbit, but rabbits don't eat marigolds. Maybe birds pecking at the insects on the plants?

any slug trails? and some caterpillars hide extremely well.

We had an infestation of caterpillars but they didn't seem to attack the veggies, just a few parsley leaves. Very few for the amount of caterpillars. The city sprayed I think, because they disapeared. I didn't see any slugs. Just ants and maybe 1 or 2 red spider- looking VERY tiny bug.