That really looks like bacterial leaf spot. Sometimes there are just black spots without the yellow halo. It's probably a mild case or just getting started. Has the humidity been high recently? Sometimes very high humidity will cause it. Do not mist the leaves, water from the bottom, careful not to splash soil on the lower leaves. Remove any affected leaves. It is a soil-bourne disease so you probably want to spray the plant with some type of treatment for awhile, but I don't know what to recommend there. Probably something with copper?