I might misunderstand, but is this issue about biome spawns? That is, the general spawn rate as you roam around? (The 10PM spawning would just be the "Night" zombie crew checking in for work.) Or are you talking specifically about the Blood Moon horde?
If it's the normal day-to-day biome spawns, then possibly you had a mod which increased that, but it broke or got uninstalled? The typical biome spawns are pretty modest (max of 4 zombies in Pine Forest downtown areas, for example, with respawns about every 8 in-game hours). I typically play my game with 4x the number of spawns more frequent respawns (via a modlet). Sounds like maybe you had something similar. If you're talking about the biome spawns.