Possible with a child theme.
function custom_page_col_width(){
global $graphene_settings;
if ( is_page(array(10,20,30)) ) {
$graphene_settings['column_width']['two_col']['content'] = 640;
$graphene_settings['column_width']['two_col']['sidebar'] = 280;
}
}
add_action( 'template_redirect', 'custom_page_col_width' );
Replace 10,20,30 with the ID of those pages.
640 is the content width in pixels and 280 is the sidebar width in pixels. You need to change those according to your design requirements. Make sure those numbers do not sum up to more than the container width – gutter width.
Untested. Should work though..