No idea at all, a picture would be handy assuming there is something to see.
I have noticed the ones I have had in quite good light are faring better than those that are in a more shaded spot,so this combined with the variable weather and short supply of sunshine might be part of the answer.
This bit on Hellebore diseases might throw light on it, even if it is only to confirm that they are not diseased, against the variable weather patterns we have had this year.
Hellebore Diseases
Hellebores are generally trouble free but in recent years some of the hybrids have been affected by various fungal diseases and viruses, e.g. Fungal leaf spot, Cucumber mosaic virus, Helleborus net necrosis virus.
Fungal leaf spot:
As the name suggests is caused by a fungus that causes brown elliptical blotches to appear on both sides of the leaves.
Lesions can sometimes appear on the stems sometimes causing the leaves to shrivel and collapse.
The best cure is to remove all the affected parts, if the problem is only slight using a fungicide can sometimes help.
Cucumber mosaic virus:
Is transmitted by aphids and causes yellow to white line patterns to appear on the leaves.
As with all virus problems, destroy the infected plant/s immediately to reduce the risk of spread.
Hellebore Black Death:
This is a relatively new disease that only affects hybrid hellebores.
It is seen as the blackening, distortion and stunting of the leaves and stems, and sometimes the flowers.
Black streaking and mottling appears as a ring spot pattern or in lines between the leaf veins.
These are eventually passed down the leaf stalks to the main stem of the plant.
An aphid endemic to hellebores is suspected of passing on the virus.
There is no cure for virus infection other than digging up all infected plants as soon as symptoms are noticed, and destroying them immediately to reduce the risk of spread.