Blinded by the Whitelighter - S3-E11
Continuity mistake: When Phoebe is looking in the Book of Shadows for information about Eames, she comes across the Belthazor page, and lays the page down flat. In the following shots, the page moves to her hand, then lying down flat, then to her hand again. (00:19:10)
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.