Hi,
The recommendable work-flow in this case would be to copy the spline for each floor and attach those together, but you can also take advantage of nested styles and make just the first floor within the Array 2S Generator in the Extend X/Y Size to Area mode and use that in another RC object (this time with a Linear 1S Generator - driven by a spline or the X Size value), where the spacing can be ajusted with the Left Padding value.
Attaching a sample scene, hope you'll find it useful.
Best regards,