I agree! The ages on the packets are just guides, mine went up earlier than the packets said, but they needed to. If she was doing fine on the stage 1 and was less gassy I would switch back for now personally. Which bottles are you using, if it's the TT closer to nature bottles you could try the vari-flow, they can be controlled by the baby, so if she does want a faster flow she can control it herself. Not all vari-flows are good for new borns though, Avent for example is very fast!
Congratulations on your new arrival by the way!
Laura