Setting a Brew persistent will make it copyable by other plugins etc.
Every copy points to the same database entry. Drinking one will not delete that entry.
Problem: Changing one potion (through brewing) changes that entry and thus changes all copies.

Solutions:

• Make persistent Potions Static, dont allow any changing
• Copy the DB entry when brewing and change the copy
• Move the whole DB to the each Items NBT storage (BKCommonlib); not Bukkit friendly; would make copying, deleting, using, etc much easier

Went for solution 1.