It could be the age. As daffs develop, the main bulb produces the new generation as bulblets, these may take a season or so to mature into flowering mode. In the meantime "the parent" bulb stops flowering, leaving you with just foliage.
My reading of your query, is that your daffs have flowered previously, therefore precluding too shallow planting or insect damage,and the fact that not all of your daffs have failed would suggest that you didn't remove the foliage prematurely.
It's nature!!