Steam heat run problem

I have a header with 5 radiators coming off a single tap 2 more radiators with their own taps further down the condensate run is closer to the multiple radiator tap and I am having problems getting steam to the last 2 radiators one of which is on the second floor. Changed radiator vent and main vent the last 2 radiators are newly piped. I have a feeling this has been an issue since they were piped. I lowered the steam pressure to 1 1/2 pounds got the steam to travel closer to the radiators. I have a feeling that I may have to be repipe back to the condensate. last 2 radiators are piped approx. 30 feet out from the end of the loop before it runs to the condensate. In other words way out in left field. I think I should cut the loop at the condensate and continue vapor run to the 2 radiators with individual taps and continue back into the condensate including these radiators on the continuous loop. Any suggestions??