Procion dyes used for cottons in home dying are fixed with sodium carbonate (also known as soda ash). This is also used to raise the pH of swimming pools. About a cup to a gallon of water. You could try soaking the fabric in that for about 20 minutes then rinse and wash. Might help. Have never tried it myself.
Dawn doesn't set dye. It keeps it in suspension in the water so works kind of like color catchers to keep it from depositing on other fabrics. And only the blue dawn.