I have exactly the same thing with Van Persie... had high hopes for him. Finally he'd been given the centre-forward position (in previous years he was nearly always moved to the left/right in favour of Van Nistelrooij or Huntelaar) and he looked sharp in the pre-tournament games (4 goals in 3 matches, scoring with both left and right foot). Then he's also Holland's first choice penalty-taker, which can be important in fantasy football.
But in the first two matches he hasn't showed it AT ALL. He looks tired, he doesn't get the ball and instead comes collecting it on his own half... and when he does get a shot on goal it doesn't look powerful. Yesterday I even thought about transferring him... yet I still have a feeling he might start scoring again. Maybe that's wishful thinking.
Second place feels good, but it also makes me wish I had read about the substitution thing earlier. Bringing in Hamsik today isn't paying off though, but at least he's not doing worse than Lahm (whom I substituted him for).