I'm pretty sure that fermenting =/= rotting. You could say that the corrupted rock stimulates micro organism activity but it wouldn't explain non organic materials rotting. If it rots everything else, why doesn't it rot the micro organisms then? Stupid illogical magic rock, stop making me angry.
I've been reading manhwas and webcomics for years but still I can't understand why has it become popular to add cooking elements to stories, its pretty useless imho