Hostile Mobs Not Spawning

So I've been making a mod which adds tons of new biomes and I've noticed that no hostile mobs spawn in any of the biomes. My custom ones do, and even vanilla passive ones occasionally. But some biomes receive no passive and all biomes receive no hostile. Some biomes have custom grasses, however no hostile mobs spawn in any biome regardless of grass block. I've even set entity spawning ad yet I still only get mainly passive.