So, the fuel is leaking from the injector rail where it joins to the injector?
I have had this problem too, but where the rail joins to the pump. It was because the rail wasn't square with the pump if you know what i mean. Un-do the nut and look how the tube line sits on the injector, if it is sitting off centre bend the metal tube so that it is sitting nice and centre in the injector. That should fix your problem.
The fuel may be coming from your tap off line (those small pieces of hose between the injectors) They have next to no pressure running through them, they just divert the internal fuel leakege from the injectors back to the tank.
I hope that makes sense