Are these plants inside or outside? In ground or in containers? Any sign of pests? If in containers what is the growing medium?

From the one picture you posted it just looks like a hydration problem. That can be caused by many things from just insufficient watering to the plants being rootbound in their containers. Need much more info please.

Dave

Hi Dave,
Thank you for replying and my apology for the delay. These plants are outside in a container where they get plenty of sun. I did not see any sign of pests, but this is my first time growing vegetables, so I may not know what to look for. I used Espoma organic potting soil mix. The container is 16" and had 20 plants. I thought that the container was draining poorly, so I transplanted the plants into smaller better draining Misco self watering containers yesterday and I see that a couple of plants have this problem. Any advice is much appreciated. Attaching a picture of the back of the leaf.