Could you please post a photo? It would help with the diagnosis.

Photos are taking time to upload. They should be there in 2 min.

Did you ever get an answer? Mine are doing that also in San Diego. They are in the ground only amendment is compost.

No and I assumed it was natural and didn’t do anything about it. But I got a good harvest from them last year before they got powdery mildew when the weather got warmer. I tried treating it but eventually the plants died.

I saved a pod from last year and they have just sprouted. I expect it’d be the same as last year. Time will tell.

This reference suggests stress+phosphorus deficiency.

https://www.agric.wa.gov.au/mycrop/diagnosing-phosphorus-deficiency-field-peas

"Reddening of stems, petioles, tendrils and leaf margins can occur, particularly if the plant is stressed."

Reddish/purplish coloring in leaves is a standard indication of phosphorus deficiency. If this happens a lot, then a soil test is in order.

Thanks Dan. The plants were probably stressed due to transplant. The raised bed was built and filled with new soil last year so it could not have been phosphorus deficiency.

I sowed them directly in the bed this time. I’ll update if I see redness this year.

Well, "new soil" hardly ensures nutrient availability. I can get spanking new soil that is deficient in all manner of nutrients. I'd get a test done. Smart move on new soil in any case.

Thank you. I will do a soil test.

I found a video by MI Gardner that explained a number of reasons that a plants leaves turn red. Phosphorus but there are reasons the plant can't take up the phosphorus from the soil. Lack of water, high pH etc.

I composed the soil over the winter with coffee grinds, banana peels, egg shells, and sawdust. My squash plants are fairly yellow and everything I plant actually is fairly yellow, except for the peas, they have a red ring around their leaves. I expect this is phosphorus deficiency, but I am not sure. Next year I will put lots of broccoli stem feelings in the compost.