Guild Wars 2

I was doing this main quest with my assasin and until some point, the npc told me to go downstairs to help another npc to kill some ooze. Now, here is the problem, I killed ooze almost 30mins and those ooze keep spawning and seem that this quest don’t progress at all. Is it requires to kill ooze for so long or is bugged? Everyone encounter this problem?

Still looking for help for this… Anyone encounter same problem as me?

You have to plug the spewing holes with the stuff the oozes drop

Where are thoose holes?