I recently was hunting for an image of a chlorotic leaf on Google and came across just the image I wanted. And by golly, it was from a website by Greg Alder - The Yard Posts.  He is a Board member of the CA Avocado Society. The topics cover the range of veg to citrus and avocado.  There are wonderful, clear images of symptoms and descriptions of causes and possible solutions.  Check it out.  Here's the one entitled "Reading Avocado Leaves":

https://gregalder.com/yardposts/reading-avocado-leaves/

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