tps drop after starting multiple dungeons

Hey there! This looks to me like an issue with your map. What I'm seeing here is that your server is struggling to load the chunks for the map. You might consider reducing the view and simulation distances, as you've got your simulation distance cranked up to 10. If you don't want to change it for your survival worlds, you can instead set up world configs in spigot.yml so that by default the simulation distance is lower, while having the simulation distance for your survival worlds still remain higher. This will also significantly improve your dungeon load times, resulting in fewer lag spikes. :)

Since I haven't heard any follow-up to this, I am closing the issue. You may open the issue again if you've tried what I suggested above and it still isn't improving the load times.