3D rotation identical control point curves with central attachment point

I’ve been asked to mill small scale pagoda roofs for a model, of the simple sort where a central attachment has the surrounding (4) control point curves drawn in Top view.

Is there a way of 3D rotating all four corner rafter curves 90° down at the same time? I’m using ver 7, with some SubD familiarity, but no experience with Grasshopper.

can you post some images to clarify?