This is strange indeed. My first impression is that the soil is droughty and the plants are lacking water or due to some other root injury the plants are not able to take up water efficiently. Very chunky organic matter and poor root to soil contact at planting can be a factor in such symptoms. It may also be that some chemical was used around or on the plants to cause these symptoms. A final thought is that overfertilization may have burned some roots causing these symptoms.
I suggest you take a plant sample and/or some photos to your local County Extension Office for them to look over and perhaps be able to diagnose more clearly.
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