So your friend gave you a division of hers/his. Did the mother plant ever bloom???
To me, it sounds like a mystery, maybe it is a mule?
Too much light may yellow the leaves (unless burn and kill), but the sheaths are usually still made.
Also, the production of the sheaths on this hybrid occurs while the plant is still in growth mode, which extends from late spring to early fall, sometimes even into winter. Then the sheaths will just sit there for many months. The shorter day length for a few months then the return of the longer day length signals the plant it is time to flower.
So I don't think not giving short light hours in the winter has anything to do with flowering in your case since your plant won't even make sheaths during the summer/fall season.
How does the yellowing on the leaves look?
Do the new leaves start out yellowish? or turn yellow slowly over time?
Is it even yellow all throughout or streaks? any brown specks? (signs of iron, mag, other element missing, but again, not likely since you are fertilizing)
---------- Post added at 11:00 AM ---------- Previous post was at 10:55 AM ----------
This hybrid, well, at least the Azur Sky, is very robust grower and great bloomer under HIGH light.
It is very likely that Silken's plant is not getting enough light. Big sized plant of this one should be flowering like crazy. I was in awe when I saw this plant in bloom at a nursery.
I grow all my catts (mostly BLCs and some LCs) right along the large bay window facing south. no curtains. Leaves do turn slightly yellow green on certain plants, but all are doing fine. I'm having the best cattleya year!
The only one I had to move away from this strong sun light was the mini cattt (Tropical Pointer) that was getting sun stroked. lol