Guild Wars 2

I’ve recently started doing Triple Wurm and I’ve done all achievements from this section but one… Mentioned in title Phytotoxin Enthusiast. No matter on which character and profession I kill that abomination that spawns field that grants buff which makes us attractive to the wurm, stand on that circle, get this buff on me… Nothing. Achievement just don’t pop up. First few times, I was thinking that this situation is caused by the fact that I was killing wurm on my main character which is guardian and thought that I had a bad luck and Aegis poped in wrong time. But then I’ve done it again and was sure that I hadn’t Aegis on me. Nothing happened, achievement wasn’t granted. Then I’ve done it on elementalist and the situation hasn’t changed – still no achivement. I’m sure that i was hit by it, I had that buff. I’m sure that I’ve done everything correctly, asked my friends who was doing it with me – they got that achievement. Any chances of making this right?