All mobs stopped spawning

Suddenly without warning the world fails to spawn all mobs - the oceans are empty of fish/drowned - no hostile mobs spawn at night. Have uninstalled and re-installed MC. Spawners seem to be unaffected. Have tried different copies of my most current world to no avail. I keep copies in triplicate online and off. Tried a previous copy from yesterday and I get hostiles (possibly already spawned when world was saved) but once killed no more spawn...

Have tried setting to peaceful and back to normal/hard in menus and by commands but still no luck

Clues: Prior to this error world file size was 91MB - went exploring the perimeter of a 4 x map and world jumped to 122MB - triggered a raid from 4000 blocks away and went back home to initiate raid - won raid and this is when I noticed the error...Will start another world on this version and report back - may just be a corrupted world ...HTH