the good news is that you have mastered the skill of consistent seam allowances.
the not so good news is that you are almost certainly stitching seams with an allowance of just-a-hair more than 1/4".
rotary rulers aren't necessarily the best tool for checking your seam allowance. because they are thick, they can distort the measure for a check like that. something about the way the light passes through the plastic ... yada yada yada.
find a thin, flat see-through ruler. when you line up the 1/4" line, your stitching should be lined up directly under the line on the ruler. if your stitching line is visible above the line - even if it's poker straight and right along the line, it's more than 1/4". like ... 7/32" ... or maybe 5/16". that teeny bit is just enough to throw off the finished size of your block.
move your needle 1 click to the right, but use the 1/4" foot as you normally do. don't change anything about that. i'll bet they come out the right size.