A search turns up another 10 posts about yellowing leaves, so here's another -- hoping to clarify the cause. From reading, it seems that yellowing leaves might be a mineral deficiency, nitrogen deficiency, change of season, underwatering. And in this case, herbicide overspray is a possibility. I'm hoping those of you with more experience can help to clarify based on the photos.

This is a Passiflora edulis Nancy Garrison in southern California, planted around May 2017. We have had a hot, dry summer and autumn. It's on drip irrigation, 3x weekly, with supplemental deep watering every few weeks. Water here is hard and alkaline. The vine got slow release shake & fees citrus fertilizer in spring, some Grow More 10-52-10 fertilizer earlier in the summer, and last week some all purpose Miracle Gro 24-8-16.

Despite the yellow leaves, the vine has been flowering and setting fruit well. It's continuing to grow, but slowly.

Yellow leaves:

New growth is still green:

Thanks for your input!