Why can't I find any wither skeletons?

I recently found a nether fortress that happens to cross into a warped forest (I don’t know if that is important, I thought it might be useful to know) and I can’t find any either skeletons spawning anywhere. Everything else that spawns naturally in a nether fortress is there, but I can’t seem to find wither skeletons, which are the one reason I even went there. Do you know why they aren’t there?

Wither skeletons always spawn in Nether Fortresses, but there are a few possibilities on why you aren't finding them.

1. The light level is too high. Wither skeletons can only spawn in light levels of 7 or less. The light level may be higher from the shroomlights in the warped tress.
2. They may be spawning in places you can't see. Sometimes, wither skeletons can spawn in closed of areas of the fortress, or rooms that you can't see.
3. They are just wandering off. If the fortress is on the same level as the ground, they could just be wandering away from the fortress.

I would try exploring the fortress and removing light sources nearby, and see if that helps.