shadow from adjacent object

this sectional couch will be the bane of my existence! but i have worked through so many problems and learned a lot, so theres that. but this is my last problem. so the sectional is broken up into pieces which are easily seen in the photos (left end, right end, middle, and corner). when i place two of these objects next to eachother i get a weird shadowing effect. i have searched everywhere and at first i thought it was because my meshes didnt line up or overlapped. i broguht them all in blender together and all vertices line up perfectly. is there anyway i can get rid of this shadowing effect when I place two of the couch pieces next to each other? it would be a bummer spending all this time just for it to look jacked up if someone has uneven lighting.

thanks!

folder containing photos & one of the package files (all have the same settings): link

drive.google.com/open?id=1vFYjeEMlUBJF1vrBU6-2_aDYKHi8Mjq5