Hi emmie,
I also have a hungry baby ( she is 7 weeks old) I put her on hungry baby milk and when i mentioned it to my HV she told me to stop giving it her because babies aren't weaned now till 6 months old and if she does start getting hungrier before then there will be nothing else to give her. I have put Eva back on SMA gold but seen as i still had nearly a full tin of SMA white i've been using it for the last couple of feeds at night as i didnt want to throw it out (HV said this was ok) Maybe try Blake with an extra ounce in his bottles and see how he gets on, if he's still hungry put him on the hungry baby milk it might be what he needs to fill him up properly. Hope that helps a bit!!
Love Lisa and Eva xxx