Honestly, I am not exactly sure of what it is because of the color of the spots. Maybe I could give a better guess if I knew more of the back story. But I would say it is a fungal or bacterial infection.The bacteria is Clavibacter michiganensis is a possible cause, and it survives in plant tissue. There is not much you can do besides sanatizing equipment before you use it. Also next season till areas of the garden where tomatoes have been grown to break up the decaying of old plants.
