Overload of chunks in the server

Hey guys,
I have been playing the Farming Valley modpack and everyone has been going lag free and smoothly. However, recently the server has started to crash upon start and when I checked logs it says 'Can't keep up! Did the system change, or is the server overloaded?' I have read other reads and have come to the conclusion that maybe the server is trying to generate too many chunks. However, I do not know how to reduce or cut the chunks from my world and any help would be great.