Just a thought here. The fuel pump works on mainting the correct DP across the injector. Since the downstream side of the injector is unchanged and you may have a potential rail pressure drop, then the DP across the injector is not where it should be - most likely low. Fuel pump corrects by trying to pump more fuel to get the pressure up, which is mot needed for the other 7 injectors.
Just a WAG. I can't see one pic while at work.