can we ask for rechecking the ors sheet in iit jee

There could have been an error from your side ( if your score has been lowered by 4-8 marks ) while evaluating your score from the official answer key. If this is not the case and you are cent percent sure that there is a mistake from CBSE's side, then try calling them on the helpline number provided. Simultaneously write them a mail explaining your situation. If there is a way out, they will surely help you with that.
All the best!