Hi there,
I bought a Japanese holly about 6 weeks ago. It is about 1ft tall. I also bought a smaller, younger chinese elm at the same time which is looking very healthy and growing well.
The japanese holly was sold by the vendor as an indoor bonsai tree. I have been keeping it in the same conditions as my chinese elm; in a very large south facing window where it gets lots of light. I water the tree generously whenever the top soil is not moist to the touch with water that I collect either from a water butt, a river/canal, or a local pond. I have been feeding the tree with Chrysal bonsai plantfood diluted in water (as per the instruction on the bottle) once per week. I have pruned the tree once - 2 weeks ago. I removed plenty of discoloured leaves and removed some branches which were crossing over and crowding each other's space. I keep a window open next to the trees nearly 24/7 and usually mist them twice a day.
Initially, the tree looked to be doing really well. It grew a good amount of fresh, light green new growth. It has also grown some small fruit which looks healthy and deep purple in colour.
However, loads of the leaves have now turned a yellowish brown and have become brittle; they fall off of the tree just by brushing them lightly. Every time i look at the tree, more of the leaves seem to have become like this, and I am worried that the tree is close to dying, which is very upsetting.
I live in a flat on the top floor of a building and it is very warm because of the large south-facing window and flat steel roof. The weather has often been hot and sunny recently. Is it possible that the tree is getting too much light? And the leaves are being scorched by the direct light of the hot sun shining through the window? Is it advisable to move the tree further away from the window?
Please can anyone suggest what I might do to save the tree, and what I can do to improve the care of my trees?
Due to my circumstances, I am unable to move the tree outside

Thank you for any help you can offer.

There are no trees from Japan that can be grown indoors. Japan have temperate to mediteranean climate. The japanese holly is from the temperate parts. It needs to be grown outdoors. Chinese elm is decidious and also needs to be outdoors.Where are your location and what are your climate like?