My mum (is deaf) struggles to lip read some of her older friends these days due to the way people’s faces change around the mouth area (especially the ornamental groove and vertical rhytids) as they get older. It leaves a thinning of the area between the mouth lips and nose - appearing less curved and fleshy when younger - and due to the lack of fat/muscle there as we age it can appear ‘flat’ or stiff.
Thankfully they still can sign to each other (though that is getting a little slower these days as the arthritis in the hands and takes hold).
Age can be a bitch - and affect others harsher than some others.