Make sure your pieces are cut accurately before sewing, and measure the block after sewing. If the blocks don't measure the correct finished size, then your seams are not accurate. If your cutting, seams, and finished block are accurate, the seams should align. In looking at the photo, it appears to me that the upper block has some fullness between the triangles and the print in the second block isn't the same size on the right as it is on the left. Of course, this could be an optical illusion. Measure each piece to be sure it is the correct size. If it is, then adjust your seams. Let us know how it works out.