Stealing Trade Secrets?

I own a restaurant here in San Francisco. Recently, a young man working for me decided he wanted to open up his own restaurant. A few weeks ago, a manager also stepped down from his position and has since started working with the guy that opened his new restaurant. As of late, they have also taken one of my chefs. The restaurant is the same cuisine as mine, and since my cook has left, I have strong reason to believe that he is using my restaurant's recipes; cooking the same food he has cooked for 15 years at my restaurant, and using this in the new one. In a sense, it's as though the person is selling the food my restaurant is famous for, and is selling it under the new restaurant's name. Is there any action I can take? I am not concerned with the people who have left, but rather the information which they have and are using.