The 1.11 patch is on the test realms!

[Walkiry]

Well that's this part of the patch notes
Using an item of a particular category will trigger a shared cooldown among all other
items in the same category.

And one of the categories includes and is on 2 minute cooldown.
Night Dragon's Breath, Whipper Root Tuber and Target Dummy.

That means only one of either Night Dragon's Breath or Whipper Root Tuber in 2 minutes.
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Ah I see! Didn't remember what the Fellwood stuff was. Interesting, thanks for the explanation :-)