Simple Boxes Drop FPS by 30

Hi,
I’ve created a procedural stair blueprint that adds more treads the more you stretch it out. The issue is though that when I use it the FPS drops dramatically.

I have narrowed it down to the treads that are causing the issue but I have no idea why.
I have tested with 17 treads on a stair and the fps is sitting at about 28. When I removed the treads the fps goes up to 57.

The mesh of the tread is a box made in 3ds Max (12 triangles) and I unwrapped the uv and then exported the FBX and put a very basic material on it (one colour) in UE4.

Can anyone please help me?

Thank you very much,
Scott

Further to the above, here is the blueprint of the tread inserting.
I can provide more of the blueprint but it is basically the same repeated with different components.

Thanks for any help.

I worked out what the problem was!
I had more components spawning in to the right (hand rails, posts, etc) on the above screen shot of the blueprint. All I did was plug it to the completed node on the ForLoop and that immediately improved the fps.
Not sure why this worked seeing as the construction script i thought only ran once when something changed and not continually. I guess it kept calculating everything even though nothing was changing.
Hope this helps someone else if they are having a similar problem with ForLoops.

Cheers,
Scott