I have been trying to grow the various orange trees viewable in the pictures attached for many years, with no good results. They are located in Palm springs, Ca., desert climate, with average high temps of 108F in the summer and average high temps in the winter of 70F. I water with bubblers on a feeding schedule of twice per day at 7am and 12 noon with 4 minutes at each time. The far smallest orange tree(Cara Cara Navel) was planted about 5-6 months ago and was luscious deep green when bought and planted. The other small Cara Cara navel was planted about 1-2 years ago and has shortly afterwards maintained this fruitless curling yellow/brown leaves appearance. Actually, when the flowering season comes, they all produce abundant flowers, nearly all get pollinated and begin to set fruit. But when the fruit gets to no bigger than the size of a pea, they fall off. I don't know what I am doing wrong. This year I gave the new small Cara Cara navel a small handful of chicken poop and the others were given the directed amount of Dr. Earths citrus fertilizer which was about 3-4 months ago. The big orange tree(about 4 years planted), which I believe is a Washington Navel, has always had yellow/brown curling leaves shortly after planting, but this year they are all especially bad. Can anybody help me with this? I have seen other full sun exposed orange trees, but they are much bigger, so again, I just have no idea what I am doing wrong. Any help is deeply appreciated and much needed. Thank you.