Why Do Some Bulbs Fail to Flower?

Yes, that is a question to which I would like to know the answer! I have four pots of Crocuses and three of them flowered well as usual, but one failed to produce any flowers at all.

Likewise, I have a pot of "Minnow" Narcissus that were great last year but this year have produced plenty of luxuriant foliage and no flowers.
I also have a pot containing 5 "Delnashaugh" speciality Daffodils. Last year all five bloomed, but this year there are only 3 flowers, and one of those (still in tight bud) looks disappointingly small:

The complex "apricot-and-white" flowers of this variety are very attractive - but I just wanted MORE of them!

"Delnashaugh"

All these bulbs were left in their pots all year after flowering and I just added a bit of fresh compost on top in the Autumn. Is it this that has caused poor performance, I wonder? Should I have removed the bulbs and re-planted them? I am tempted to believe that this is the reason, but then why were my "Tete-a-Tete" Daffodils so good, when they were treated in exactly the same way?
Do you have a theory on this? If so, I would like to know it please.