I haven't battled any of the bosses in over 24 hours because I was focusing on nurturing. I decided to go seek them out and fight them and they all appear to be missing. I've even tried checking over the entire zone to see if they moved and exiting and re-entering the zone. No luck. Just to be sure it's not an image loading thing I've even moved to the spaces where bosses had been, trying to see if I just wasn't seeing the image for them. There's nothing on the map. No bosses. No chests. Nothing. Is this happening to anyone else?

For the new explore system, if you "Exit the Zone", you will reset all of the spawn points back to full duration.

Just re-enter the zone and wait a few hours (from when you last Exited... if you exited a long time ago then you shouldn't have to wait).

But they were gone before I exited. I exited to try and fix it, thinking maybe something hadn't loaded right. I didn't exit until after the problem started.

EDIT: Looks like it did fix itself. Not sure what happened though, since the issue happened before I exited the area, not after... but it's fixed so that's all that matters I guess.