What Causes Perfectly Healthy Plants To Have Curled Leaves?

Question

The leaves don’t die or turn yellow, they just curl. And not all of them!

Answer 1

Curled leaves can indicate a plant is under stress. The type of plant isn't mentioned, but these articles should help:

https://www.gardeningknowhow.com/houseplants/hpgen/curled-houseplant-leaves.htm

https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-leaves-curling.htm

https://www.gardeningknowhow.com/ornamental/flowers/begonia/curling-begonia-leaves.htm

https://www.gardeningknowhow.com/edible/herbs/basil/basil-leaves-are-curling.htm