Well, if you turned in the middle of a row and reknit some of the sts, that would actually be over 2 rows, so that's close to a quarter inch if your row gauge is 7-8 rows per inch.
It looks like your BO is tight in the picture on the left, that could account for part of it, and maybe your tension changed as you went along - looser at first and getting tighter about halfway through. The lower edge seems very even from the CO edge to the end of the stripes, then seems to 'shrink' in. So maybe you were knitting looser during the color changes and tightened up later.
sue- knitting heretic