Processed salads would be store bought salads that went through commercial machines to chop the vegetables up, add flavors, and them package.
Even buying a homemade salad from a local chef may depend and may or may not be considered processed.
Though… a salad made from vegetables processed in a food processor may be an issue. It may need to be a processor reserved for Pesach food and use only.
Maybe not having a Jewish Torahdik person overseeing the processed Pesach food preparation is like the Cholov Yisroel chumra?