Trining Lamprey and Normality Gas

So the title explains what my largest issue is right now. I'm making my way into the deep jungle and encountering trining lampreys. I delt with the twinning lampreys in Bethesda Susa easily enough; but my new issue is keeping all of the lampreys in the normality gas long enough to kill all three of them. Does anyone have advice for for more open areas like the baroque ruins?