Answer: It sounds like your tomatoes' leaves have suffered some sunscald. This happens when greenhouse-grown seedlings are suddenly placed in full sun. Just like Northeasterners who travel to Florida for a week's vacation in February, these plants have almost no natural tolerance for intense sun, and are easily burned. To avoid this problem in the future, you need to "harden off" seedlings before planting them.
Hardening plants off acclimates them to the elements of wind, temperature variations, and sun.
I usually put my seedlings out for a few hours in a sheltered spot (out of the strong wind and sun) for a few days, and gradually increase their exposure over the course of a week, based on how they are adapting.
Your tomatoes should recover if you plant them soon, mulch them and water/feed them with a liquid seaweed/kelp fertilizer mixed as directed. Bury the stem right up to the first set of leaves, and new side branches should start to grow. Best of luck!
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