Minecraft slows down dramatically when I am on soul sand, under the effects of a night-vision potion and being blasted by a ghast

I was in the Nether going ghast hunting, so I drank a night vision potion so I could see them. Unfortunately, when I drank the potion (while on soul sand), Minecraft started running really slowly, almost stopping completely at one point. This made me panic and run into lava and die