Barbardn, welcome to GoY.
All flowering plants produce seed to regenerate themselves, this is the purpose for plants (and animals) to live. However, it takes energy from the plant to produce ripe, viable seed and this is taken away from next years flower power. In the garden we don't always need lots of new seedlings to weed out so, if we remove the dead flowers of daffodils, the bulb does not put energy into producing seed instead, this energy goes to the bulb to make strong flowers for next year.

once the flower has died of you can still break the flower and the bulbous bit just below the flower off and you still will get flowers next year.
Because eventually the leaves will die down.My parents did this for goodness knows how long and we still had a good show of daff's each year

The bulbous bit your talking about is in fact the seed pod. By removing it, as said above, the plant puts all its energy into producing next years flower instead.

This what I have done for years.

But this year have daffodils blind just leaves no blooms.

Do I lift these and discard?

A good feeding regime might bring them back, Scotkat, but could take a year or two. If you are not talking about too many then this might be the opportunity for a change of wardrobe, in a manner of speaking?

Its not all of them just some BH.

What would you recommend to feed?

If they are in the garden, then liquid tomato feed for a quick snack and bonemeal for a longer term feed.
If they are in containers, then tomato feed every week until the leaves have died back and then repot them with fresh compost.

Thankyou must admit I have never fed my daffies:)

We only feed the ones in pots. We have not had blind ones in the garden, but there are so many that we might not have noticed :-(