Q2- I have the following BLACK curves + the PINK curve (not dense). I loft them all (Black and Pink) and created the surface I wanted. I am happy with the form but I see like a LINE kind of artifact. I tried rebuilding all the curves and lofting them again but that artifact stays. Is there a better way to form that shape? What am I doing wrong?

NOTE-
- The shape or position of the PINK line can't change as it has to match another seperate piece.
- The blue lines were not used for lofting or anything, it is just used as a guide.
- The shape HAS to come to a flat surface where the vertical blue line is. As it has to match a seperate piece which is flat too.

Thanks :-)