Finding rows that are not duplicate
Pretty straightforward:

select e.* 
from EmployeeFile e
inner join
(
  select FNAME, LNAME, DOB
  from OriginalData
  group by FNAME, LNAME, DOB
  having count(1) = 1
) o
on (e.FNAME, e.LNAME, e.DOB) = (o.FNAME, o.LNAME, o.DOB)