Are they puckering when you press them after they've been appliqued...I'm new to machine applique but have done hand work for a long time... If both your fabrics weren't prewashed, then steam can make them pucker...or too hot of an iron. One of the reasons I prewash everything...even tiny scraps I aquire from garage sales etc...i put them in a zippered mesh "personals" bag and gently wash them by hand in a dish tub. then hang them to dry by clips on hangers. Then when I press after appliqueing they don't pucker.