Does it look like it's drowning?

While the plants below it thrived, the tree kept losing its leaves. It was gradual. It seemed seasonal. I could not tell if I was over-watering or under-watering. Unfortunately I had the automatic drip linked to an existing irrigation circuit that fed all the mature boxwood shrubs at the other side of the driveway. Adding a new circuit was way too much work. Turning down the water kept causing the old boxwood to yellow and dry out. Boxwood is slow-reacting, too, so each trial-and-error test took months to interpret. After each experiment, I had to dial it back up to normal for the sake of the old shrubs.

At this point the tree has been in the ground for 18 months, and it's still struggling.
Pittosporum undulatum or Victorian box or Cheesewood.