I think it's a matter of driving style. Seb' has always used as much and more of the track width as he could get away with. The Red Bull of his champion period was very compliant and some of the design tweaks and "advantages" allowed him to take liberties with kerbs and the like. This year he has had to reign in his propensity to exceed track limits, due both to the changes in the technical rules and also the enforcement of track limit constraints. In particular he is having great difficulty adjusting to the ban of the EBD (which Red Bull had perfected more than any other team) and having to manage the torque. He can't just pin the throttle pedal anymore and let the ECU do the work. Maybe he doesn't have as deft a foot as we thought.
Nevertheless, Seb' was very much more in the game at the weekend but, as well as being screwed by the safety car, his consistently running wide to defend against Hamilton led to his spin which ultimately damned his race. He's far from burnt out and as the reliability and power unit issues become resolved we'll see him close in on Daniel. I think Ricciardo will still outrace him because Vettel is perhaps too aggressive and too greedy - i.e. uses "too much" track - and IMHO the current formula doesn't suit his current style. If he adjusts that style to suit then all bets are off!