Soft Grey Tulip Bulbs

I had this problem with a whole planting of new Cream Jewels a few years ago. Some kind of rot, I suppose. They were planted in a spot with not good drainage, and I lost all but a few of them. In fact, the ones that were planted a little higher in the same bed have just now been dug up and are nice big hard bulbs.
I found this same symptom in one group of tulips this year. I threw them all out. They were dug a bit prematurely, but I have done the same with other tulips that I needed to move and just left the leaves and stems on as they dried out.
Any idea what the problem is?