Mobs rarely spawning now. I cannot find any mobs.

At night, mobs are not spawning at night, there is like 1 monster spawn at night every night. But it's rare to see the mobs spawn in groups. I'm not sure if this is a bug, or if it's something about the update. If so, please fix the mob spawning rate... It would be very helpful because I need some of the drops that they drop.