[Quest] Cannot complete the quest "A Sample of Slime..." after turning in "...And a Batch of Ooze"

I picked up the quests "A Sample of Slime..." and "...And a Batch of Ooze" from Chemist Fuely in Undercity a few days ago. For both quests you're supposed to gather slime samples from Ooze-mobs, in Felwood for the first one and in Un'Goro Crater for the second one; and then you're supposed to turn them in to some kind of bowls on the table next to the quest-giver which are called "Testing Equipment", there are blue question marks above the two bowls. That way you're supposed to get the quest items necessary for completing the quests.

If you read the titles, it's pretty clear that the first one is also meant to be the first of the two quests, even though you can pick them up at the same time.

Anyway, I had gathered the materials needed for both quests, and I used the Testing Equipment for the second mentioned quest without any problems; and without thinking too much about it, I completed it before turning in the first one. The blue question marks above the Testing Equipment then disappeared, so I couldn't use them to get the needed quest items for the first mentioned quest, and therefore I cannot complete the first quest.

I'd really like to complete that quest for Undercity reputation, otherwise I wouldn't really care that much about it, but I also think that it would be good to fix it so that no one else will encounter the same problem in the future.

I wrote a ticket about it in-game, and was told to rename or delete my cache folder and see if the problem was still there; otherwise I should post it in the issue tracker. I tried the cache folder-thingy and it didn't change anything, so now I'm posting it here, hoping this is fixable.

Thanks in advance.

Emil

In-game: Doomster