Can you provide a close up?

Here's a closer look at the damaged leaves

Looks like something ate the surface tissue some time ago.

I would like to know what that is. Mine is doing that and has lost leaves as well.

Looks like a chemical sprayed on the leaf when the temperature was too high

I agree with John, it looks like some sort of liquid did that. Some of those splotches might have also been created by trauma (like from thorns).

It might be chemical damage but it looks to me more like physical damage like possibly wind damage.

Graham, was this tree sprayed? When did you get it? It may have been damaged before you got it.

If the brown spots are no longer appearing or getting larger, then I would not do anything and not worry about it.

I got it about two months ago. I believe it was sprayed right before it was shipped. It was totally green and healthy the first month and only developed the brown splotches in the second month

Follow up: should I remove the damaged leaves or leave them on the tree? Thanks for all the help y'all

Update: in the last three weeks, basically all the damaged leaves originally pictured (i.e., along the main trunk) turned yellow and then fell off one by one, starting from the bottom of the trunk up. The branches still look good, but I'm not seeing any new growth or blossoms yet