Trunk soft on Adenium Arabicum
I'm new to this forum, and am hoping I can get some help/advice. I purchased an adenium arabicum from the Toronto C&S club sale this June. It's my first adenium, so no prior experience. It's sitting in an east-facing window, with full morning sun (live in an apartment, so no option for a south-facing window).
After about a month, I noticed that an occasional leaf would turn yellow, then eventually fall off (about 1 leaf per week). I also noticed the trunk felt a bit soft, but wasn't sure if this was a change from when I first purchased it.
I did some research and found that it might be due to over-watering - although I also read that a soft trunk could be due to under-watering. I figured over-watering was more likely the problem, so I drastically reduced watering to about once every three weeks from about mid-July until September.
Despite the reduced watering, there has been little change to the plant - the occasional leaf still turns yellow and falls off (though the frequency seems to have decreased), and the trunk feels about the same. The plant seems more-or-less the same as it did in July. The trunk has a bit of a depression on one side, but otherwise seems to look okay.
I've pulled the plant out of the pot and examined the roots. There is no bad smell, although some roots (towards the bottom) do seem dried out and brittle. Soil looks like a mixture of regular potting soil, with some extra perlite and sand (I think).
Hope to get some advice on whether I'm over/under-watering, or if this is not an issue with watering at all. For the first month, I watered probably about once a week, and fertilized with 10-52-10 every two weeks, as instructed by the vendor I bought it from.
Also, I've been holding off re-potting it until spring, but am wondering if perhaps re-potting into a faster-draining soil mix might be helpful at this time?
Will try to add some pictures to help with visuals. Thanks in advance for any help!!