Google "Flea Beetles" as I believe they are your pests in question. There are a few chemical treatments for them, though their damage tends to be mostly cosmetic and they tend to move on as the season progresses (from my experience). If you look on the plants, search them carefully, you may find a few small beetles on the plant - when you do, feel free to crush them, that is also effective :)

Almost looks like flea beetle damage to me. Have you noticed tiny black insects that jump off the plant when you try to kill them?