If they fry aren't stressed, then they probably will not get it. Most fish actually naturally have ich to some degree. Stress lowers the immunity of the fish and allow the ich to take over and become a problem. One of the key factors to treating ich is to identify the source of stress. In such situation, my malawi tank. 2 of my malawis have developed it in response to the aggressiveness of my Red Zebra. I have taken the Red Zebra back to the LFS as there was no improvement in the sick fish because the Zebra was chasing them trying to attack. Hopefully now that the stressor is removed, adequate healing can begin.
Have you been monitoring your water parameters? Bad water quality is also a stress inducer.