Sheryl - tomato plants can be susceptible to fungus and bacteria and without a close up of the leaves, it is challenging for me to hone in on a possible source of the problem.  I am including a link to an article below that will provide you with more details and pictures of disease symptoms.   

To narrow this down look at your plants closely and assess as indicated below:

*Leaves - wilting, spots, location of spots, shape of spots, yellowing, etc.

*Plant - where did the symptoms first occur - et al. at the bottom of the plant, top of the plant, specific areas on the leaves, etc. Was this a gradual process or occur fairly quickly?

https://extension.umd.edu/resource/key-common-problems-tomatoes/

From the picture you sent and the overall plant decline, I am thinking the cause may be Fusarium wilt or Early blight.  Fusarium will progress gradually while blight can affect a plant quickly.  Both are fungal in nature and easily spread when the conditions are just right.  Usually that means warm, moist rainy days and nights.

For future planting years, it may be wise to look for plants that are known to be disease resistant (which should be indicated on the plant tag).  Link below with more details on varieties.  

https://www.vegetables.cornell.edu/pest-management/disease-factsheets/disease-resistant-vegetable-varieties/disease-resistant-tomato-varieties/

Hope that helps!