We have been growing tomatoes for years and over the last few years have had trouble with them dying off after planting from the bottom up. It seems to be a bug that crawls into the stem. Leaves die off at the bottom at the beginning then further up as the season progresses. Plant eventually dies.
Certified GKH Gardening Expert
This could be insect or a fungus issue. If you are having this same issue and are planting in the same location you may have a soil issue.
Crop rotation is recommended to help avoid these issues.
I'm listing a few articles that may help you pinpoint the issues and help you have better results in your next growing season.