Are they limited to one per character/stat?

Now that i reached Grandmastery in Alchemy i was looking forward to putting all those ingredients to use and go crazy on the perma stat boosts. However, they seem to work only once per stat and character.

What is up with that? Is this intended?

Dangit. And i can't even remember who had what type of potion so far... back to trial and error until everyone's filled up, i guess. >_>