Plain sawed lumber is more susceptible to cupping than quarter sawed lumber and to add to the problem it's common to only apply a finish to 1 side when unfinished raw flooring is used. With the quality of wood flooring we have today you may be real fortunate with only 2 being cupped. What i'd like to see for a solution is replace those two but that isn't always possible.
Are the problem planks located in an area that could possibly have a enhanced moisture issue?
EDIT: EDIT:
Are the problem planks located in an area that could possibly have a enhanced moisture issue?
EDIT: EDIT: