Start your investigation by looking for aphids

In all the years that it has occurred, I've never seen anything on the plants - aphids included. There's certainly nothing to see at the present time.

Whitish specks visible in the two photos here probably aphid exoskeletons. Look at the affected areas with a magnifier before you decide there is nothing there. And do it early in the start of the damage.

Leafhoppers can do a lot of damage too.

where are you.. and can you rule out cold damage?

btw: ... if you see it at the garden center.. pick up the plant and carry it to the boss.. and ask them what it is

Cold damage does not cause leaf contortion.

Leaf distortion is also affecting Hydrangea and a Rose bush. On the Rose, distorted leaves are Aphid-free, but some leaf stalks on the same bush are covered with Aphids, but the leaves on these stalks are normal. A complete mystery.

Ken, Mike is in London, England,. From your point of view they don't know the meaning of 'cold' there. 32f might happen once or twice per winter.

thx flora .. a much better answer than the others ...

i never thought of taking pix after a cold event .... but i can think of a frost/freeze on an emerging hosta pip ... which distorts and kills the outer leaf.. and then the inner leaf.. in a week two is incredibly distorted.. trying to grow thru and out of the previously cold damaged leaf ...

but she says it never happens.. so i must be wrong ... and so must every single person at this link ... go figure: https://duckduckgo.com/?q=frost+damaged+hosta&t=ffcm&iax=images&ia=images

ken

ps: are there really nurseries that sell aphid infected plants in GB???

or these FREEZE damaged : https://duckduckgo.com/?q=freeze+damaged+plants&t=ffcm&iar=images&iax=images&ia=images

or these FROST damaged: https://duckduckgo.com/?q=frost+damaged+plants&t=ffcm&iar=images&iax=images&ia=images

or COLD damaged: https://duckduckgo.com/?q=cold+damaged+plants&t=ffcm&iar=images&iax=images&ia=images

or cold damaged plants with leaf contortion: https://duckduckgo.com/?q=cold+damaged+plants+with+leaf+contortion&t=ffcm&iar=images&iax=images&ia=images

The typical symptoms of cold damage are drooping, curled, shriveled, discolored or dry, brown foliage. Contorted growth of new leaves - the most tender and vunerable portion of the plant - would be extremely atypical! Those would most often appear shrivled or discolored, not contorted. And we've already determined based on location that cold damage is highly unlikely, however you believe it may be manifested.

And I have no idea why you would assume that these plants were purchased as aphid infested. Aphid populations can come and go extremely rapidly, as is evidenced by the OP claiming to see no sign of them on his plants currently. The same thing can happen in a nursery setting (although they may also treat to control) but the distorted foliage will persist untll removed.