Newborn babies. Of major concern.

Hello doctor, this is Anil from Delhi. I have twin girl babies born on 13-Mar-2018. The babies were born premature at 32 weeks and were admitted to NICU level 1 for observation for 2 weeks. At 34 weeks we got discharged and everything was ok as of now. Weight at the time of delivery was 1.700 and 1.800 and now it is 2.230 and 2.340. Babies' all blood reports at the hospital were normal. Now the topic of our concern is that the babies faeces are green in colour since 2 days. They, seems like, have to exert pressure to do bowl movements. I've attached two pictures of the same. The feed is normal with frequency at regular 2-3 hours. Their sleep pattern also appears normal. They do not cry excessively, but only at the time they are hungry. We haven't got tested them for jaundice yet but their skin appears normal red to pink colour. Please doctor, take a look at this and let me know if there's actually a problem of major concern. Thanks for your time.