Hi, 

The eligibility criteria for neet states that a UR candidate needs to have min 50% aggregate in PCB in std 12th and passed every subject.

For SC/ST/OBC the min requirement is a 40% aggregate in PCB and passing marks in every subject.

There isn't any specific decreament in the aggregate for obc ph candidates. However the qualifying marks after neet will have considerable decreament.

All the best