Quite a few recent questions about this with daffodils. Leaves on for about 6 weeks. Feed. Too shaded. Or just to annoy us! Also suggest you scroll to the base of this spread, and click on D and see what more expert persons than I might have said.

And there has been a problem with blind daffodils this year... possibly the summer wasn't hot enough last year to form the bud. But you do need to leave the foliage to die back naturally and feed once a week with half strength tomato food.