Is it necessary to change to follow on milk at 6months? DD is currently on aptamil first milk (she's 4months). Have asked my HV advice about this but she was very non committal, and said it was up to me, that she'd 'probably' be fine on first milk to 1 year old. However the ads say it has extra iron extra so am I denying her iron by not switching?! Any advice would be appreciated 