Pretty quilt. If it were mine, I would add more in the 6 inch blocks. Personally (and this is my "thing"!) I don't like any sagginess in the block after the quilt is washed. I would do 2 lines down the rail in each block, maybe with a regular stitch instead of the decorative stitch.
If you don't add anything else though, your quilt will be lovely and just fine!