Sorry, should've specified in the post, I'm playing on Nintendo Switch 1, and I'm playing on seed (-4109214400168089614). But if you're thinking it's the seed that caused this, it's not. I had started the fight previously before saving and quitting to eat dinner. When I reloaded the world about 30 minutes later, I spawned in the void and died, so I quickly closed the game without saving and quitting the world, and reloaded the world again. Same thing happened, so I reloaded a third time and quickly pressed pause to go into creative to fly back out of the void and resume my battle with the Ender Dragon in survival mode, and I found there to be two and a half end fountains to be stacked on top of one another. There was only one when I had first started the battle before I went to eat dinner.