Salam sis! Alah, jangan stress sangat lah, some babies just develop slightly slower in one or two measurements but normal elsewhere, and your air ketuban okay, heartbeat okay, semua vital signs green light. Honestly, makan lebih pun boleh try, tapi growth discrepancy ni usually bukan sebab mummy tak makan cukup je; it's more about how baby ni grow pattern dia sendiri, especially if first baby mu dah 2.75kg dan baby ni estimated 2.3kg, maybe just slightly smaller frame je. Best lah you check back with your doctor at next scan to see if the gap is staying the same or growing, kalau consistent je and baby okay, most doctors aren't too worried, but they'll keep monitoring closer now until you deliver. I'd really suggest bringing this up again with your OB and maybe ask for a specialist opinion if you're nervous, just to be sure you're in good hands.