6 seats may not be avbl & partial upgradation cannot be done, thats why 1st pnr was not upgraded whereas the 3 seats may be avbl in higher class & 2nd Pnr was upgraded. In 1st Pnr, your 2 pax were confirm, next 3 got 3 empty seats at charting & last one remained waiting. Now even if there was 1 more seat avbl in higher class, railway wont upgrade just 6th passenger. Either all on a Pnr or none.