A struggling tomato garden often results from a missing detail or two, among them too little sunlight (less than 6 hours daily) and/or inadvertent water shortages, even though only briefly. Then, too, the kind(s) of tomato you used may have complicated the issue. Begin your search for answers by reading “Grow Your Own Tomatoes and Tomatillos” (https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec1333.pdf)
You can obtain a complete soil test from A&L Labs; (503) 968-9225. Call them to ask how to package and submit your samples. When you submit your soil samples, include details of what you did for soil preparation, fertilizer, watering practices, and anything else you think may be useful and, then, request recommendations for a home garden. For instructions to collect the soil sample, see “A Guide to Collecting Soil Samples for Farms and Gardens” (https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec628.pdf)
Good luck in your garden!