I have twins who was born after 31.5 week pregnancy by cesarean section. They stayed inside incubator for one month. They are 3 months old now, the second twin has started stretching her neck backward as result of colic or cramp as I note if there is another reason I don t know. The twins are fed by infant formula (artifitial milk) S-26. the second twins starts stretching her neck backward for 6 hours every day, crying as well, I want to know is this as result of lacking some digestive enzymes or there is another problems, I make her burp after feeding her, I used feeding bottle that prevents gas entering beside anti-colic medicine, but I don t see any results, what should I do?