It is the policy of the Keystone-K as well as the other major agencies that triple washed leafy vegetables must have the supervision of a reliable kashrus agency. Triple washed leafy vegetables that bear one of the major reliable supervisions may be used. The same brand may be found with and without a hechsher at the same time in the same store. If they do not bear one of the major reliable hechsherim they should not be used without checking. You may contact Rabbi Eisemann to find out which supervisory agencies are accepted by the Keystone-K.