Moving locations of major, secondary gridlines

Is there a way to change the location of major, secondary vertical gridlines?
My data points, associated with the secondary vertical axis, do not fall in
the right position on the chart. Rather than falling in the middle of the
individual categories on the x-axis they are offset randomly to the right or
left. The data points seem to fall on the major, secondary vertical
gridlines so I was hoping I could move them. Thanks!