My tomato plant is heathy all around, but this tomato (which is also the largest) is developing brown spots. Not familiar with growing tomatoes. Any suggestions on a potential cause?

Can't tell from the pictures of that is insect damage or not.

Newyorkrita, is there a way for me to check if it is an insect?

Are there actual holes in the tomatoes or just soft rotten areas?

If there are holes it is probably insect damage.

Just soft rotten areas. Seems like bruises. Thankfully no holes.

So either sunscald or soft rot. Sunscald is basically a sunburn and not much of a problem. A tomato might get it here or there but just pick and discard. Not catching.

Soft rot caused by a bacteria. Pick any affected fruit and bag and discard. Not in the compost pile but in the garbage. If lots of tomatoes affected not sure what one can do.

Bacterial soft rot
https://plantpath.ifas.ufl.edu...
https://hort.extension.wisc.ed...

Intheswamp said:
Bacterial soft rot
https://plantpath.ifas.ufl.edu...
https://hort.extension.wisc.ed...

Ed, that really looks sad!!

Newyorkrita said:

Ed, that really looks sad!!

Yeah. That image is off of the University of Florida's website. I'm sure I could find something similar in my garden, though.<sigh>