Alamak, yang ni memang biasa happen dekat newborn especially dalam first few weeks, tapi since dia dah muntah enough to get admitted, kena observe betul-betul lah. A few of my mum friends pun ada babies yang reflux teruk at that age, and usually it's either feeding position, overfeeding, or immaturity of the digestive system, tapi since the hospital wants to monitor, I think terbaik you follow up dengan paediatric specialist dia, jangan tunggu lama. In the meantime, try feeding in upright position, smaller frequent feeds, dan hold baby upright 20-30 mins after feeds, tapi definitely check back with your doctor sebab at 24 days, kena rule out anything serious. Semoga baby gets better soon!