A number of things can account for the symptoms you've described.  If you reply to this message and attach sharp close-up photos, we'll try to help.  However, we might not be able to diagnose the problem by viewing photos.  Sometimes laboratory analysis is required.

In any case, control measures for the three most common leaf spot diseases are the same.  The following publication discusses these diseases and how to manage them.

https://extension.umn.edu/plant-diseases/tomato-leaf-spot-diseases