This is curious since daffodils are quite hardy. I suspect that either the winter was unusually wet, especially if your soil is heavy, and they rotted or an animal used them as food. Other possibilities are that they are overly crowded and need to be dug up and divided and that they failed to replenish the bulb because foliage was cut back too soon. Every year you cut them back a bit early- that is before they turn fully yellow, you are cheating the bulb of what it needs to survive the winter and send up shoots the next spring. It is also wise not to plant daffodils where you have flowers or shrubs that need a lot of supplemental watering. If you dig up the clump, you can probably figure out which of these problems affected your daffodils. When replanting, make sure the bulb tip is planted 6-8 inches down, or roughly 3 times the length of the bulb.
