I have had this happen before,  with other veggies too, I found it to be Earwigs  aka pincherbugs. they only go in to the garden at night so chances are you wont see them unless you go out late with a flash light.    I use a product called "Dead line" its used for snails but kills alot of other bugs too. I made a circle around the plants so nothing crawling could get in and it dont have to come in contact with the plants at all. dead line is a liquid