Look, I'm not saying simply nerfing them out of the blue would be fair or right, it wouldn't.
A fair way to do it might be for Hoof to make an announcement, that on (for instance) the 15th of december all of the currently overpowered inventing potions will be reduced in efficacy. That way you can postpone releasing the new inventibles till after that moment, and people can still get plenty of use out of their existing potions?