Answer: Unfortunately, plants stressed so severely may or may not recover and thrive. (It is possible that they were stressed at some point prior to planting and would not have thrived regardless of anything you did or didn't do.) First off, I would examine the planting bed carefully for any inconsistencies or external causes for the problem. (Was the soil preparation the same, if you use an irrigation system is it working correctly, if you used fertilizer did some of them get a double dose or no dose, that type of thing.)
Basically, it sounds like they have failed to root into the surrounding soil. If that is true, they are strangling themselves at the roots and suffering drought stress. You might want to dig one up and see if the roots are still growing in just the original potting soil from the cell pack. If so, about the only thing you can do is try to untangle a few roots and replant it. Be sure to water it well the day before and to water them in well after replanting, and treat them like brand new transplants until they take hold.
I hope this helps!
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