Eugenia Brush Cherry

I got a Eugenia Brush Cherry bonsai as a gift, about a month ago. In that past little while it has been losing leaves. The leaves are green when they shrivel and fall off. I had noticed some new buds where the old leaves had fallen off, but now the ends of those branches are turning black. I try to keep the soil moist, making sure it isn't soggy, and other branches still appear healthy. Can anyone tell me what might be wrong with it?

Try letting it get drier than "moist." They need LOTS of light; a window won't do.

Is there anything I can do to save the branches that are blackening?