How strange I to have the very same gggggr as yourself being Alexander as well. My family also all origonate from St Monans where my father still lives to this day being James Fyall Hutton Guthrie. Peter and Ann also had another daughter Janet (b1837 d1916) who lived her whole life in the village. She married a William Guthrie and they had 5 children that I know of and it is this line and the fyalls that I am researching.
Good Luck