So what happened is that you did not read Alchemist's hint.
The Alchemist cures two cards to his left and right(4 total).
8 is two cards away from 6, 8 was adjacent to a Pooka.
8 was corrupted by Pooka than cured by a Alchemist.
Plague Doctor corrupted 2 as you can see from the image.
Corrupt Abilities happen before you start revealing cards.