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Planted 12 tomato plants in a raised garden. They look really good - tall healthy plants with lots of early fruit. A few days ago, one plant's leaves on the ends became very limp and days later leaves began dying. Plant looked sort of stunted. I uprooted it and discorded it. Now another plant is doing the same same thing. What is the problem? How can I keep remaining plants healthy? I live in central Louisiana.

Are you watering it enough? Tomatoes need to be watered at least once a day, if not more, especially in such warm weather.

A couple pictures of the problems would really help!

If it wilts and dies over the course of a week it could be phythotora. How well does the soil drain and how high is the water table. It will only affect plants once the root gets deep enough and it happens more in summer when the water in the soil is more stagnant. The roots would look rotten when you pulled them up.
https://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74133.html

If it is phythoptora you can only plant shallow rooted plants there. Plant tomatoes in pots in potting soil and raise them off the ground on a bench or bricks. Pots also work better if you have tomatoes that are not resistant to nematodes, but you have to make sure you keep the pots clean and do not contaminate them with plants, tools or hands.