Used Karma - S6-E13
Continuity mistake: In the scene when Piper is fighting off demons by herself at the start of the episode and Phoebe and Paige come to help her, she narrowly misses a fireball and jumps down to the ground to dodge it. In the shot before, her forehead is un-injured, but as she dives to the ground you see that she is already bleeding from her forehead, *before* she actually hurts it. (00:02:30)
Used Karma - S6-E13
Continuity mistake: In the scene when Paige and Piper are doing first aid on each other, Piper makes quite a production out of the business of peeling the backs off band aids to apply to Paige's arm - but when she slaps it on Paige's arm, it's a non-adhesive white 4 x 4, which Paige has to hold on her arm with her other hand.
Used Karma - S6-E13
Continuity mistake: At the beginning, Piper is wounded on her forehead by the demons. When they orb out and orb into the kitchen Piper doesn't have a wound on her head anymore. (00:03:25 - 00:05:40)
Answer: That was a mistake in the series.
Also, the episode is called 'Babies First Demon' and this alone tells us that it's Wyatt's first time in the field (so to speak) and as the sisters say, they've done a good job of clearing up their own magical messes so far. Nobody really knows how advanced Wyatt's powers are, or will become. That's why the cleaners appear, to nip things in the bud. The Cleaners didn't want to chance that the sisters could clean Wyatt's magic up, just incase they couldn't. Therefore intervening themselves, just in case.