Aptisyp Syrup

My daughter is 2 years old, from 14 aug she is having nausea and vomit at night only, she is fine and active in day time. There is no other symptoms like fever etc but she is not taking enough food except mother's milk. From 16 aug, we stared syp ondem 5m1 twice a day and syp ranidop pd 2m1 twice a day. On 17th we gave iron syp also, on 17th and 18th she had loose motion also 3 times in a day, doctor prescribed syp zifi (50 mg/5m1) 1 ml twice a day and darolac z sachet and stopped icon syp. Loose motion is settled down now, but she is still having nausea and vomit at her sleep and on night only. 1. My question is what could be a cause of nausea and vomit and why it is happening only in night? 2. She is not taking enough food, what should we give her to eat?