What is wrong with this mikan tree?

All of the mikans have these brown marks. it’s this trees first crop. They also, so far, taste pretty watery . My other mikan trees in a different section of the garden have no such markings and taste great.

Mikan is a seedless Mandarin hybrid often sold in the U.S. as Satsuma tangerine.

The fruit in the lower half of the picture is simply under-ripe, typical for this time of year in my location.

The blemished fruit above has symptoms of a bacterial or fungus infection. You can determine the difference by wiping the discolored area with a sponge. If a good portion of the brown material comes of easily then it is a fungus, otherwise it is a bacterial infection affecting the peel.

The lower fruit is from a different tree.
The bad fruit won’t wipe off, so it must be bacteria? What kind?
The section of the garden this tree is in gives me a lot of mysterious problems that I suspected may be something in the soil. The kiwi vines next to it lack vigor and always drop their fruit just before ripening. Tomatoes and peppers will develop some kind of leaf bacteria(?) and die early. Only watermelon seems to do OK there.
Then mikan tree’s leaves etc. seem to do OK otherwise.

I think saying “the soil is bad” is too general. It might be harboring disease, or a plant there is a disease host, or it is traveling there (wind borne) from nearby.

The tomato trouble could be related but the kiwi problems might be circumstantial. Lots of things come to mind for early fruit drop.

For your citrus, consider spraying with a product containing Azoxystrobin.