There were bigger problems in that tree than an "off" (but hey! Sourced! Not a geni error!!) birthdate.
The first and a big one was separating Marjorie, Princess of Scotland from her sister Margaret. Then worked on the rest of the siblings. Should look a bit better now.
I don't have a greatcsolition to the birth date issue as its in line with her sibs. The marriage date is validated as cited by Crawley.
http://fmg.ac/Projects/MedLands/SCOTLAND.htm#_Toc253996204