Other mistake: At the beginning of the episode, when the mermaid goes underwater, she holds her breath.
Siren Song - S5-E4
Other mistake: When the siren gets the pole that was speared through her pulled out, there is only blood in the middle part of the pole. If it had really been pulled out of her, it would be bloody all the way along. (00:19:55)
Other mistake: If all the objects in the fortress are originals from the fairy tales, why are the ruby slippers red? In the original story the slippers were silver, they were made red for the MGM movie, so they would be the brightest thing on the screen.
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.