change the size make it bigger first of all
easier to see details
see pic i did here
can you encircle the areas with problems
i can see some white around some corners but i think this is because of the specular and mirror reflection you have
also you do have a spot light lighting from the back with high energy level that could be creating some bad reflections on the model!
also the floor has some mirror which will reflecft light back to the bottom of your model !
this does help and may be the cause of bad refelctions on bottom!
see pic here
one thing i did not do a lot of model with curves but can you explain something
you seem to have only one curve here !
how can you make different areas with only one curve?
i tough you could not do that with cuve in blender!
see second pic i remove some of the floor mirror and lower a little the spot enregy
hope it helps