What can I do about my daffodils that did not bloom?

http://www.walterreeves.com/gardening-q-and-a/daffodils-buds-wont-open/

where do you live? did they grow, bud, but not open? it's called Bud Blast from weather most likely too much rain will do it, just let them die back and then snip only the bud off,let the rest die back naturally they will come back next year.Give them some bonemeal in the fall mixed in soil. Also if you cut them off before they go back completely into bulb naturally they will not rebloom

Yes exactly what Lynn said. 😁

There are many varieties of daffodils, some bloom as early as February others as late as May. Perhaps you have late bloomers!