@NorfolkLiz,
This is not something I've seen on violets around here (yet) and I hope I don't.
The type of damage looked like what is often seen with leafminers.
When I did a search for Violet leafminer I found this ID request:
https://bugguide.net/node/view...
Evidently the poster (in Maryland) is satisfied this is a leafminer but does not know the identity. Leafminer damage can often be indicated by tearing the damaged leaf. The upper and lower epidermis will be mostly intact, leaving two papery layers with nothing in between but leafminer droppings and maybe shed skins.
This may be a relatively new pest arrival. Your local Extension Service might be interested in receiving a sample. Include some old damaged leaves and some green ones with stippling and small tracks possibly indicating currently active miner larvae.
Without an exact ID it is hard to be sure how to treat this, but if this showed up in my garden I would try to take a pre-emptive strike with some imidacloprid granules.
Then after allowing a few days for uptake, I would remove and destroy all the plants in that area to try to help control spread.
Please keep us advised!
Pat