Hi everyone! I've never had a bonsai tree before, and I got a jade bonsai about 2 months ago. Since then, it seems to have been in steady decline, with a lot of leaves falling off. We've lost a good part of the leaves now, and recently small branches have started to fall off as well. It came with a tag that said to water it every 5-7 days. I tried to do some research online and found that overwatering is a typical problem, so I've been watering about every 7-8 days. When I water, I usually do it until there's a bit of water dripping out into the drip tray and then stop.
We have it right in the window, but I'm afraid the lighting's pretty poor because we have privacy curtains. So about a month and a half ago I got this little plant light https://www.amazon.com/gp/product/B00005 ... ge_o01_s00 for it, which I leave on for about 8 hours or so every day (sometimes longer). The light doesn't seem to have made a difference.
I know that something's wrong, but I can't tell if it might be root rot or if I'm underwatering it. The soil tends to seem really dry to me when I stick my finger in, but I've read that root rot is a big issue for these plants. I was going to repot it and check for root rot, but I couldn't find the right kind of potting soil locally. I've never done much gardening, so I'm a bit wary of repotting it if I don't have to, just in case I hurt the plant more than I help it.
Based on the pictures below, does anyone here have an opinion on whether underwatering or overwatering could be my issue? Or maybe something else entirely? I'm a bit lost, but I really don't want to lose my first bonsai!