JoAnn's has some decent fabrics, some very nice fabrics and some we won't mention - I will not purchase their fat quarters, for instance.
Since you have already bought fabric, you have two options. Return it if you are concerned. Uncut, unwashed fabric can be returned - at least it could when I worked there in the 90s. I personally would not return less than a yard. Option two - my choice - would be to wash, dry and press the fabric and then make your decision whether it is quilt worthy. I have made some quilts that I feel are nice with fabric from JA or HL. I have one thin piece from HL in a quilt on the machine now. I had to have just that color - I am confident it will be all right once it's finished and quilted. It's sewing up nicely - no stretching or anything.