i would divide them. Sounds like they are not getting enough nutrients. A feeding of bone meal will help too.

Good luck!

While they still have leaves, I'd try a fertiliser that's fairly high in potash.

Wood ash could be useful, but not if your soil is naturally alkaline.

And a topdressing of good old compost wouldn't hurt at all, so long as the ground is damp when you apply it.

It appears they have been there for many years because of the spread of bulbs but none of them will develop flowers.
If they have been there for many years, they undoubtedly are quite crowded, and need dug and divided. You can either dig/divide them now while they are in the green, or else wait until the foliage has died back and yellowed.
Either way, it will likely take them a couple of years to recover and grow enough to be blooming size.

Sue

Is the hyacinth id certain if they have never flowered? Could they be Spanish bluebells? The midst of a hedge doesn't seem a very likely spot for someone to have planted hyacinths.

thankyou all for your advice. these bulbs probably fronted the back portion of this hedge since there's a border edging in front of them.
But forsythia arches and the stems readily root so I think that's why the hyacinth appear to be amidst the hedge.

I think while they have plenty of blooming time sun and very healthy looking leaf growth and leaf covering from overhead trees, they probably are a bit too low in the ground so I will lift them this fall, bring them forward to a
better area and set higher in the ground.

I presume if the leaves are full height and no evidence of a flower stalk coming then nothing I do now will bring forth a bloom this year. Next fall project. Thanks again.