This is one of the reasons why you want to avoid washing a top before it is quilted. Washing a quilt top places a lot of stress on the seams.
What I would do at this point is use iron-on interfacing on the wrong side to stabilize the seam areas that have opened up (of course pushing the fabric together as much as possible). Then I would either sew strips over the seams or add applique over the opened seams as others have suggested.