So today i installed Lithium and Phosphor in my Minecraft mods folder for performance boost and stuff. Every world that i previously had or created was running smoothly, except Emma's end practice map. For some reason while playing on that map i was facing severe lag spikes and Fps Drops. Does anyone know what's wrong?

find the armor stands and break them. the easiest way is to look around until you find the lag spot and break them

Thank you @Eyeball It actually worked!!