i was rewatching the series due to the new season when i came to natural born wesen. sean ingests the potion meant to cure him and juliette from the zaubertrank. so part of the cure was nicks own blood. shouldnt a zauberbiest have lost their powers after ingesting the blood of a grimm like adalind did? (if this question has been answered already please link me to it)
Well, yeah, they just showed Rosalee pouring the liquid from the bottle where Nick's blood was into the second cup. But that's not to say that she already poured something from the bottle into the Captain's cup. After all, they kept on referring to "they" as opposed to "she" before the blood was taken from Nick. So there is the assumption that both of them would be drinking the concoction with Nick's blood. Rosalee also said in an earlier episode that the solution involves Juliette and the Captain doing something together. Nobody said it would only be Juliette. It was always a reference to both. It was implicit that they were drinking the same concoction.