Catts: Sheaths, no Sheaths in Same Cultivars

[JMNYC]

Hi.

Over time, I've noticed some of my standard Catts which bloom more than once a year, seem to produce buds with no sheaths in winter on new bulbs, and same cultivars (2 as of right now, one on 3 bulbs) produce sheaths in Summer on new bulbs.

Is this a known phenomenon? If so, is it the temps which impact this? Day length? Something else?

Thanks!