My guess from the photos is that it needs Nitrogen, it may also be deficient in something else, it looks like Magnesium deficiencies to me based on the leaves, though I would not expect to see that in the calciferous soils that are commonly found on the west coast. Soil pH effects nutrient uptake, so the first thing I would do is do a soil pH test, get home pH test kits for under $10 in most garden centers. This includes a small capsule of powder that you mix with a soil sample and water then compare colors on a chart. Do note if you have recently fertilized the soil it can throw off the readings if your soil sample is contaminated with any granuals of the fertilizer. (Don't trust he cheap electronic probe pH meters).
If your soil pH is above 7 I would suggest the first step being to fertilize with a fast acting Nitrogen source, my first choice would be Ammonium Sulfate, available at better garden centers, Amazon, etc. Just be ware it can cause fertilizer burn if used too strongly. Or Calcium Nitrate if soil pH is below 6.5, though I think the chances of this are VERY low for southern California. If you want to stay Organic use Blood Meal as a fast acting Nitrogen source, though it is a little slower acting than the other two mentioned above.
If you do need Magnesium, common unscented household Epsom salts are a great source of it, you can probably add a bit without much chance of overdosing, if you want to try just sprinkle half a cup of so evenly around the tree.
p.s. if your pH is above 7.5 or 8 you may also have Calcium induced Iron Chlorosis, the solution is to add iron using something like ironite, and lower your pH over time through the addition of Sulphur, this is a long slow process though.
Q