They just took longer this year to die back; sometimes the foliage does hang on for quite a while. I'd cut it off at this point in the season, looks ripe enough to me.

Are they definitely daffodils? The focus is poor but the leaves seem strangely sharply pointed.

You can cut daffodils down from six weeks after blooming.

They are

Floraluk, is the 6 week rule counted from when the bloom opens or when it fades? I made the mistake of planted hundreds of dutch master daffodils in my front gardens - they bloom big and beautifully very early but then fade before anything else has grown to cover it and the beautiful thick green leaves just grow and grow and grow to nearly 3’ tall! Last year I had had enough and cut them back at about the 4 week mark after the flowers faded and they came back beautifully and a few had multiplied. I wondered if I could get away with an earlier cut back next year!

From when it fades. And the time was set by the RHS so is designed for the UK. Possibly it varies in hotter climates.