I think they still be considered as  Nuia. Different morphologies and sections orientations. 

I agree with Dr. Carrera, that these look most like Nuia cross sections. Numerous authors have indeed allied these with algae, albeit often as "problematic."

These fossils are Nuia, in different sections, considered a problematic micro-organism, or for some authors, as an oolitic structure.

I agree with the others. Its Nuia.