I planted this fuyu persimmon at the end of March, on a fully exposed sunny slope in San Diego. It was mulched and watered every 2-3 days depending on the weather. (click for larger images of leaves)

At the end of March, flowers appeared:

But now, the tree has lost some leaves, the remaining leaves have yellow borders and some are mostly yellow.

It is on the same watering schedule as a lychee and wax jambu and asian pear that I planted at the same time, all of which are thriving.

I tried watering with Foliage Pro weakly weekly for the last few weeks trying to reverse whatever is happening, with no improvement. The mulched soil is moist underneath. Am I watering it too much, too little?

Any thoughts as to what the problem is and how to fix it? Or should I give it some benign neglect and not worry about it?

Measure your soil moisture level with a meter.

The dry vegetation nearby isn't watered, they are native grasses that are really more like weeds (and potential fire hazards if they grow any bigger)

Gotta irrigate in san diego, we've only had a total of 6 inches of rain and estimated evapotranspiration of 20.6 inches since jan 1.

I usually err on the side of watering more if there is any question since its dry here in socal, but i will give the moisture meter a try