Hmm. Is it abrasive terrain or just simply damp? It isn't as bad as I envisioned...I am not sure what I expected.
If you are going after any thrush aggresively, then there is nothing more to do on that score. If it were in part due to thrush, it will have to regenerate.
Were they ever "full"? My mare has very narrow frogs, she has never been shod or tender footed and she can make it over rocks just fine. She has lived in lush pasture, rocks, and sand and their shape size never changed. Anyway, when hers shed they appear to get even "narrower", only because the shedding part gives them the temporary illusion of being a bit thicker.
For comparison, this is an old photo, but as you can see from the "tab" on the top, the frog was about to shed. Photo742.jpg