Hi I Was Giving Dexolax Milk Powder To My Twin

Hi i was giving dexolax milk powder to my twin kids.now as they have gained weight i.e. 3 kg each doctor said to shift to lactogen 1 .but i am facing problem the kids are not able to digest it .as there stol clour have changed to green in colour and it smells bad and watery .please suggest what to do. They cry a lot after givung milk