Hi Bonnie, 

  If in trimming the leaves you are not eliminating a large proportion of leaves that is a good idea.  Disinfecting the tool should also be done. Without seeing the spots, it is difficult to say what the treatment should be; however, if it appears to be a fungal or bacterial, applying a copper-based fungicide is a good idea.  Fungicides work best as preventatives but in most cases, this will at least slow the progression.  Avoid overhead watering. Check out the following links:

Tomato leaf spot diseases | UMN Extension

Controlling Tomato Leaf Spot Diseases | Horticulture, Landscape, and Environmental Systems | Nebraska (unl.edu)

I hope this helps.