On many of the vegetable plants that I bought this year, the leaves have curled up and are hard. They look twisted and hard, and they have stopped growing. What happened and why? This has happened with my cucumbers, tomatoes, and peppers. I bought them all from the same place. I replaced them and the new ones are fine.
Curled Vegetable Leaves
Certified GKH Gardening Expert
It may have been a potassium deficiency. No one is really sure why plants need potassium, but they do know that when they don't get it, they become stunted and deformed among other things.
Just to be on the safe side, add some green sand or other potassium rich fertilizer to the soil.