Suspicious Slurpee
Remi used [Blizzard] to make snow so that she could turn the potions into smoothies.
Nobody said no to berry flavoured smoothies.
While Remi was confident, Thor had been listening to the parts of the conversations which related to ruining someone's potential with too much of a good thing. He trusted his little sister, but she got too enthusiastic about her projects, and she didn't study humans much.
There was a risk that like the first day's Royal Rank soup, this was going to overwhelm them, but because this was a potion forcing them to gain power, it might cause permanent damage.
[Just wait, you will soon see that I know what I'm doing. It's even in the book as a safe advancement formula for baby Elites.]