They need to do something drastic ,

Ghostbuster style , close all of them for 24 hours , clean everything with clean room white suit crew from a company that cleans hospitals ,
then 12 hours of fumigation,

throw ALL food away , put in ultrasonic cleaners to clean plates , knives forks spoons etc, on and on.....

then the top Execs will only eat at Chipote for 1 month ,

OK....its never going to happen , but since they have no idea where the problem lies they need to start at Square 1