All types of mobs are not spawning in world (not on peaceful)

When I created the world and played for a couple days, all types of mobs from hostile to pets spawned at a balanced rate, but now it is like I am playing on peaceful difficulty. There are no mobs passively spawning on the surface or in the oceans anywhere in my world. I cannot find anything from an enderman to a squid. When I try to reset the spawns by going from peaceful in my settings and saving, and then back to hardened difficulty, the mobs spawn at a balanced rate but for only one night. Are there any permanent fixes to this mob passive spewing issue? Thanks!