Watch that potion bug!
Potion Brewing Queue slots may disappear after collecting a Potion and immediately attempting to brew another Potion. Exiting the Potions section fixes this issue.
Ouch! Didn't realize that what this meant.
I collected a potion, started my nightly brain and nothing appeared. (The plusses went away.)
So, being me I hit the brain again. Then two brains showed up in the queue.
Be careful out there folks!