Sorry for late reply, but I just stumbled upon this thread today.
Scilla peruviana requires a sharply draining soil, otherwise the bulb will rot.
I suspect the 'mushy' bulb is an indication of rot. You should use a very lean mix, maybe one part planting mix and 2 parts grit - coarse sand or gravel. I'm not sure if your bulb is salvageable or not. I would replant it in a lean mix and hope for the best.
