I finished watching the finale recently, which I kind of liked, but this season was absolutely sub-par and I'm guessing they must have had a lot of budget cuts. Many of the stories seemed to be more of a personal nature, where they could save money filming in their building, etc. Regulars left the show or were killed off without any reason, other then I'm guessing money. Some stories like Carlos' in Episode 12 were just kind of shoved, thrown out and forgotten about with a simple, "he made it back."
I don't even understand why they bothered filming season 4 if they knew it was going to be so half-assed.