Do you have Home Extension in your County? IF so, you might want to take these leaves to them; they will have a better knowledge of what it might be in your area.

Always take diseased plants to a nursery in a plastic bag and wash your hands after handling them just in case there's a fungal issue.

when was the last time they were fertilized, how often and with what fertilizer?

What are your high temperatures? Could be sun scald.

I haven’t applied any fertilizer to the plants. They were planted in an established bed with a mix of garden soil and compost. I’m in NJ. Temperatures have mostly been in the 70’s with a few days recently in the 80’s and turning hotter this weekend.

Yeah looks like leaf miner, I think, maybe

The wiggly tracks look like leaf miner damage.

it is heat scald temperatures are obviously to high.