It looks like the sizes of diamonds vary. Measure the width of the inside row and the outside row. They look different in width. Check the pattern directions for the correct measurement. Then you know which strips to fix.
Did you cut individual pieces or use strips? Did you perhaps turn the ruler and use the side with the extra 1/2 inch marking when you cut them?
Here is a tutorial that shows some helpful tips.
https://www.youtube.com/watch?v=KNyISYL5ZIg
If you need additional help, lay the ruler over the strips. Line up a seam line with a mark on the ruler and post the picture.