Apple tree issues in southern CA

Hey fruit lovers. I have an apple tree. It’s a grafted tree with 3 kinds of apple on it. My zone is 10a. I water the tree once a week. Some of the leaves are looking very sad and I’ve not been getting a good crop (as I did the first year I had it). I use with organic fruit tree fertilizer. I did recently fertilize it as the leaves looked like it was needed but not sure what’s causing the black/brown edges to the leaves? Any ideas?
app tree 2

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Welcomes back Sally,
This is what I read about your symptoms
Why are the edges of my apple tree leaves turning brown?

Why are the apple tree's leaves turning brown

Potassium is critical to tree vigor and growth, and the formation of apples is known to pull a tremendous amount of this nutrient from the tree. One of the symptoms is browning leaves, although this typically happens later in the season. Even so, a lack of potassium
I would suggest that even though you are watering, your soil moisture profile may not be keeping your feeder roots moist enough to enable metabolism of the fertilizer you are providing.
One way to test my theory would be to mulch your tree very well starting with a very this less than 1” at the trunk but thickening your mulch out to about a foot or so beyond your tree drip line. At the drip line the mulch should be about 6-8” thick. Keep it very thin until you are a foot away from the trunk. Let it go that way through next season but fertilize with a balanced fertilizer starting as soon as buds are swelling next spring. Hardwood chips are best but a thick layer of leaf mulch would also suffice to help keep moisture regulated throughout the growing season. Do not try to grow grass or lawn wishing the mulch zone I described as it will only Rob nutrients that your tree needs.
This would be my best way of solving your issue.
Good luck
Kent, wa

Ok thanks Dennis I’ll try that!