As you say you have traced the farm back to 1618, I'm presuming you have found and seen records of sasines outlining this.
(It would have been helpful to say in your post just what records you have, to save those wishing to help you going over the same ground again).
Have you looked through all the records on
https://scotlandsplaces.gov.uk/?Lots of historical tax rolls (actual images), that may mention your family.
Were they non-conformists and part of the Covenanters movement in the late 1600s? Lots of information about them to be found on-line.
Did they take part in the battle of Drumclog in 1679? Again. lots of information about that on-line.