So i've been seeing that zombies are spawning in like Minecraft zombies, is there a way to fix this issue?

Thats what the zombies are in Rust, placeholders.  The zombies people use are murderers and scarecrows in different costumes.  But murdereres were just removed from the game.

so does that mean that plugins such as plagued murderers no longer work?

None of it works out of the box anymore at least.

That it the way the original plugin had the zombies when it came out , way before any other plugin had anything to spawn, i still  use them because they are sneaky, make no noise and when you are busy looting a drop or scoping out a possible raid they come behind you and drain your health,

** edit , apologies to HumanNpc dev (which came out 6 months before but my server host had trouble installing it)

dam, rust really messed up a whole bunch of plugins