A nice spring would be a slow one that lets everything bloom in its own time. Two of the last three have suddenly erupted into a bout of summer temperatures in late April or in May. That caused some of the greenhouse bulbs to shut down for the season before they could produce enough of a bulb. Probably mostly because I was away over a weekend and did not get the greenhouse walls off to increase ventilation. This in combination with some unusually early, long and hard winters has reduced my pot grown bulb collection considerably. The outdoor/garden ones have fared better, under snow.
I used to have only a "frost guard" electric heater running in the greenhouse, without fan. It kept temperatures a bit warmer tha outside, but with -25 Celsius outside it still fell to around 15 below inside. The sand beds and pots still froze solid for long periods, and I tended to kill my more tender bulbs like Sternbergia, Colchicum and some Crocus and Narcissus. They looked just like yours in a recent Bulblog. Lilium, Erythronium and Fritillaria seem more hardy. Now I have installed a heating cable, and hope the future is brighter. To late for my Sternbergias, only one S. lutea seems alive so far. Also the cable has an internal thermostat that turns off at +5 C which might be a bit high.