The long- term stability studies (25 ± 2 °C/60± 5%RH ) and the accelerated stability conditions are (40 ± 2 °C/75± 5%RH ) are performed using three drug substance batches. If the stability result of one of three batches has a significant change during the stability testing period in the accelerated studies, what actions should be undertaken? (“Significant change” for a drug substance is defined as failure to meet its specification.)