Maybe plants don't go really dormant, but most bulbs do. If you do not respect their dormancy (rest) period, you kill them. Perhaps your Cyrtanthus 'Venus' is not a hybrid between species but a selection of C. mackenii, of which there are several stunning color forms. That it is evergreen and tolerant of shade points in that direction. What you did is basically right: if the plant felt like going dormant leaves would start going yellow and then brown. If the plant were really trying to go to sleep and watering was not discontinued the bulb could rot from the roots up. Now that you see it remains green water must not be discontinued whatsoever although in winter new leaves will not be probably produced until spring.