Q.What “bug” Is Destroying My Plants?
This spring I bought basil plants, bee balm, and dwarf phlox. Shortly after that I noticed holes in the plant leaves. Then it spread to other plants. It seems like it may be a type of flying insect. I do not see caterpillars or worms. Did I import this from the nursery that I bought them from? Or is it a more common problem this year? (I have never seen something like this before.)

Certified GKH Gardening Expert
I does appear to be insect damage, but I am also seeing signs of saturated soils that do not have time to dry out between watering. This will exacerbate any insect damage, dramatically.
I don't see the insect in question, so I can't identify what is causing the issue.
Make sure that the soil has a chance to dry out between waterings, at least, down to 2 or 3 inches. Normally, rain water is plenty. If there is a drought, watering may not be a bad idea as long as you confirm that it is dry down to an acceptable depth.
I would recommend a broad spectrum insecticide, and a fungicide. They can, usually, be used together. Sometimes the ingredients, even, overlap.
Here are some articles that will help:
https://www.gardeningknowhow.com/special/organic/what-are-organic-pesticides.htm
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/special/organic/biofungicide-information.htm
https://www.gardeningknowhow.com/garden-how-to/info/homemade-fungicide.htm