Sick or sport.

Cyrtomium-falcatum-distorted-2-1.jpg Cyrtomium-falcatum-distorted-0.jpg

I have two self-sown Cyrtomium fortunei, 4-5 years old that appeared on my tufa rockery. Since being relocated 2 years ago to an established shady raised bed that is filled with enriched (multi-purpose compost) London soil they have produced sparsely bladed fronds with contorted pinnae.
Is this disease or am I growing up a rather ugly cultivar?

If disease, can it be treated, or would euthanasia be a better solution? If it’s a cultivar, does it have a name?