So I dont know how useful this might be now but let me explain something apparently everyone missed, seemingly forever ago. This mini is what a Derro use to be. Basically a Derro was a Caedimus who went succomed to madness from their unknown diety. The Monster Manual for DnD should have told you that or the Bestiary for Pathfinder. When a Derro gets cured of his madness, he turns back into a Caedimus. I think his Charisma drops by at least 6 and his Wisdom increases by the same amount.
Long story short, They are Caedmius, not Derro. They become Derro due to madness.