I have a digbyana that was divided several years ago. One has 5 blooms working for this winter, the other has one yellow dried up sheath. They have both been grown the same and given all equal right to the light. I dont know the answer and if anyone did then growing plants wouldnt be growing them it would be raising them like children all perfect ladies and gentlemen. Most of us know that doesnt work either
maybe 1 plant got more roots hey? All I can think of.
And another reason why some grow 100's of plants and then start picken them off one by one till they down to the last few worthy perfectly grown plants. 1 out of 10,000 is more like the percentage of worthy plants.
( a lot of us end up with these plants that were picked thru and already determined were inferior dont ya know. thats why 90% of my collection is going into the trash this winter. its all crap.)