I'm new to designing with surfaces so naturally I watched some youtube tutorials and in many of them they are able to effortlessly merge several complex surfaces and then thicken them with no issue. I am designing a mask and I am not able to get rid of the contour lines that appear at the edges of the surfaces when I knit them together. Nor am I able to thicken them. I tried playing around with the splines themselves to reduce the curvature as many other posts suggest with no luck. Maybe some one here knows a way to cleanly merge these surfaces. Attached are a .zip of the file and a couple images of the design.