What method are you using to feed? What ratio of feed? Top feeding, open feeding, frame feeder etc? How many frames of bees/brood in this hive, Keep in mind the division of labor in a hive and are the nucs strong enough that the caste of nectar collectors is strong enough to meet the demands of a growing hive. By now a nuc started in July, even a 2 frame nuc, should be a full hive. Is the queen laying a good brood pattern? Something is certainly amiss. Are your other hives able to rob these nucs? These answers will help everyone figure out how best to help.