Cannot Reproduce (Horde)

Objectives
Koltira aboard Orgrim's Hammer wants you to use the Partitioned Flask at each of the 3 cultists' cauldrons at Aldur'thar, then bring it to Chief Engineer Copperclaw.
 * Blue Sample Collected
 * Green Sample Collected
 * Dark Sample Collected
 * Partitioned Flask (Provided)

Description
I smell their cauldrons from here, but that's not plague they're cooking.

Pledges to the cult are forced to drink a concoction that steals their will and enslaves them forever to the Lich King.

Some say the potion contains the twisted soul of a being who was tormented before being mercilessly slaughtered, but I've never been able to reproduce it...

Fill this flask with a sample from each of the three cauldrons in the northwest region of the gate and bring it to Chief Engineer Copperclaw.

Rewards
You will receive:

Progress
Whatdya got there, ?

Completion


Ahh... I know just the thing!