Cavespiders, Slimes, and wolves not spawning at all.

Not sure why I am not getting any of said mobs in my world.

I am in 1.81, using Craftbukkit 1248. Below is a list of plugins.

http://pastebin.com/itXzyM8v

Essentials has all it's respective spawns setup properly, and so does Regios. Not sure what else could be the culprit. Advanced mobs was added after the fact (added it thinking it would help).

They can still be spawned manually via a command but... I don't ever see them in the wild, same goes for silverfish actually.

Anyone had any ideas?