I got this bonsai as a gift, and it came in the mail from Amazon. I was a bit skeptical of it's health and have no experience with this species (it's a Fukien Tea as far as I can tell). Some of the leaves started turning yellow slowly, and they started turning brown. Not sure if it's an environmental issue like too much/little water or sunlight, or maybe a disease of some sort.

I have two pictures here of that same area on the tree taken about five days apart.

I would appreciate any help or advice, thank you!!

Hello
I recently purchased a fukien tea aswell
And I had the same problem.
So I read on it and I found out that It could either be the watering or the position it was in .
I knew it wasnt the watering as I was doing it as I was instructed so I moved the tree from a windowsill that was open all the time to my room that is a loft room so the window is on the roof
And since then no more falling leaves and loads of new growth
Regards
Nico