Sever world corruption

Me and my friends started a small vanilla anarchy sever everything was going fine but yesterday when i logged on a bunch of chunks where missing and mob spawning was buggy (IE zombies and skeletons spawning where spawning in daylight and pigs where spawning over the corrupted chunks and falling into the void pls help i am playing on vanilla 1.21.1 

For anyone how wants updates i will post some on my Youtube channel https://www.youtube.com/@ThatMinecraftShrew

and if u can help pls leave a comment