Plot hole: When Grams is summoned for Chris's wiccaning, she reminds Piper of "the talk" they had when she was a teenager, about how important and special being a witch was to Grams and how it would be to the girls someday. But in the first episode, the girls have no inkling they are witches, and when they find out it's passed through the maternal line, they wonder if Patty or Grams was a witch - suggesting that they aren't sure or have no memories of them as witches. I know there was some memory altering at certain points, but why would Grams have a conversation specifically about how great it is to be a witch and then erase that?
Charmed (1998)
1 plot hole in Cheaper by the Coven
The Importance of Being Phoebe - S5-E11
Continuity mistake: When Phoebe is lying on the ground and is supposed to be unconscious, when Cole goes to pick her up you can see Phoebe throw her arms around his neck. (00:29:15)
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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.