Hi,
Without knowing a bit more it is difficult to be certain.
Tenancies in Scotland were changing at around this time and were starting to get more expensive. This drove a lot of people to both move and emigrate. Many of my Deeside relatives emigrated, albeit slightly later. There are a lot of books and other resources on the subject. It is complicated. Bear in mind also that the big landowners had land all over, so a tenancy might become available a long way from where you might expect.
You haven’t said where you found out about Grace, was it on Scotland’s People if not have a look there as it may give the farm name.
Also how certain are you of the link Rothiemurchus?
I have come across cases where baptisms or the records were a long way from the place of birth. Deeside and Fife, for example.