A photo would help greatly.

All my perennial wallflowers, just out of nowhere, have been munched by brassica stem weevils in the last month. The damage looks the same as flea beetle damage, but the weevils are matt dark grey, 2-3mm long, with a tiny white speck on the upper back.
Took me forever to identify the critters, they're not that widely reported on the internet (or maybe it's just my rubbish searching).