20w21a - Wither Skeletons and Blazes Not Spawning in Fortresses

When I went to my nether fortress to try and kill wither skeletons to get wither skulls, I noticed that there were no wither skeletons or blazes spawning. Usually my fortress is swamped with blazes and groups of 2-3 wither skeletons, but absolutely none of either spawned unless I was standing next to a blaze spawner. I noticed that the biome labeled when I pressed F3 was nether wastes, but I don't know if it's supposed to say nether fortress. Can someone please help me? 20w21a 5/20/20 10:55pm EST