If baby is gaining well and has sufficient wet diapers, don't worry abt it! 7.4kg for a 3 mo is healthy! My baby was just 5.8kg at 4 mo, he's at 25th weight percentile, not balanced with his 75th percentile for height. As comparison, my boy was taking 180ml per feed mixed FM and BM but cldn't gain as much even tho he was 3.6kg at birth. So I think ur baby is growing well even with the reduced overall intake. Just monitor longer and maybe feedback to ur PD in the nxt appt.