New to fruit trees

Hello there. Just recently moved and am in zone 8b. Property has some dwarf fruit trees and some are in a green house. Avocado is drying ( found out I’m not watering enough) and the  jujube is turning yellow. I’m finding it may need some fertilizer. I’ve never handled trees before and am still a novice gardener. Any advice is helpful. There are lemon, lime, barrette pears, red delicious apples, grapefruit, oranges to name a few.   I truly have no knowledge of pruning and fertilizer care. I did purchase an orchard book that is packaged somewhere I cannot find of course!

Any recommendations for books or sites that simplify this?

Thanks for any help.  

https://www.google.com/search?q=new+to+fruit+trees+what+do+I+do+to+maintain+them&sxsrf=ALiCzsYCSQikRh3rkUAlPs4LmK3EcdQ3bA%3A1659161075937&ei=88nkYorqOIaOseMPmMK7iAs&ved=0ahUKEwjKr7nU-J_5AhUGR2wGHRjhDrEQ4dUDCA4&uact=5&oq=new+to+fruit+trees+what+do+I+do+to+maintain+them&gs_lcp=Cgdnd3Mtd2l6EAMyBQghEKABOgcIABBHELADOgQIIRAVOgcIIRCgARAKSgQIQRgASgQIRhgAUM4SWMo7YJ1IaAFwAXgAgAH_AYgB1hySAQYwLjUuMTKYAQCgAQHIAQjAAQE&sclient=gws-wiz#kpvalbx=_JsrkYvfgOMmbseMPuMeFiAM25

how-to-maintain-fruit-trees

For Jujube go to https://aces.nmsu.edu/jujube/