I purchased a healthy-looking plant 12 days ago, took it home and repotted it the same day in a mix of roughly 75% cactus/succulent soil and 25% perlite. Within 4-5 days, it was starting to droop noticeably. After ten days it looked like a mess. Then yesterday one of the three stalks folded over on itself and appears to be dead/rotting (soft to the touch). I haven't watered it.
I had a another dracaena marginata in the same place with the same soil a few months back and it also started drooping within about a week. I did the exact wrong thing and watered it, which quickly killed it.
At first I thought this was just the plant undergoing the stress of repotting and acclimating to the new conditions. I figured the solution this time was to hold off on watering. But the new plant died anyway, and even quicker.
Is it possible that late afternoon direct sun is killing it? I'm in Phoenix and the plant is located in front of a large west-facing window. Outside the window is a covered porch, so there is only direct sun late in the afternoon for a couple hours, but it is intense. Across the room is a large east-facing window, so this location is fairly bright all day. The plant at the nursery was indoors with no direct sun and artificial light.