Doing some more research, it appears this might be a case of bacterial blast (or citrus blast). I first noticed this after cool, very windy weather. The pictures I saw online are more advanced, but perhaps with time mine will look like that. Doesn't appear to be any real treatment for the leaves already affected, just containment. I'll probably cut the damaged parts off.

On second thought, it may not be citrus blast. It has the black petioles, affects younger growth, and was precipitated by strong winds. But, some online sources say citrus blast usually requires significant moisture (e.g., prolonged rain). Definitely haven't had that in Phoenix. So looks like I'm back to the drawing board on what this could be.

Looks like a tear in the leaf from the wind. Don’t worry so much about your trees, the more you baby them the more harm you will do. I have seen it happen hundreds of times by many people on this forum, folks worry themselves into over caring for their trees and end up doing more harm than good. I’d move your trees out into full sun for the next 6 months, it’ll do wonders for them.

Evan

Thanks Evan! I can believe the leaf damage is from wind, but what about the black petioles? I've never seen that before.
I do run the risk of caring too much for the trees. Believe it or not I've gotten better than I used to be 🙂.

same, wind damage. It’ll lose those leaves but don’t fret, it’ll probably put on another growth spurt before it gets too cold and grow some leaves better suited to cooler weather and less UV.

Thanks Evan, good to know the wind can do that. I'll stop fretting now 🙂.