Texture along Rusty Bars

Hello Blender artists!

So, I’m making a fan art scene and I’ve been struggling with texture for the bars of my rusty metal fence,
From afar it’s all fun & games until you start noticing the repetition happening every other few bars.
I kinda want to see the rust spread randomly throughout the fence.

I’m using nodes (Cycles render)
I tried using the Random output (Object Info), but it didn’t work at all.

These are my nodes for the fence:

I mix the black metal with the rust (using a grunge texture mask which is a group, image below)

Does anyone have any tip, suggestion on how to achieve what I need for this scene? Tried looking everywhere.
The bars are all part of this single object (fence).