With ice on the wings it is very normal for stall speed to go up, stall characteristics to become worse, and overall lift v drag to become worse.
There have been several crashes of Jets in the states where the pilots have not carried the recommended extra airspeed and have stalled on approach (whilst on the dry wing recommended approach speed).
I would have thought rather than tailplane icing it was just the natural degradation of wing performance, flying the approach at close to your undocumented stall speed and then stalling it in rather than flaring. A good thing it happened a couple of feet above the ground rather than 100 feet above the ground.