Tellabella,
Your fabrics are stunning. The quilt looks beautiful.
Here are 3 Sharon Schamber videos (some have 2 parts) showing how to whip (nicely) a block back into shape. Watch them - especially the stretching and truing - and try to apply what she does on the block to the corners of your quilt.
Truing a block:
http://www.youtube.com/watch?v=v-3RIWhBvcA
Stretching a block:
http://www.youtube.com/watch?v=sQkF02vpVuw
Shrinking a block:
http://www.youtube.com/watch?v=lIjZqABo2NY
Barnbum used these tips on a Bargello that was out of whack - like 2", and it brought it back into shape.
Starch can be your friend. Just be careful not to scorch your quilt top. I don't think you have to take off any of the borders, but if you don't fix it now, it will just get more out of whack as you add more borders.
And wow again. It's really gorgeous.