In the two years that I worked as an RN at a hospital nursery, we had one baby get full blown GBS. Mom was pos, of course, her water had been broken over 24 hrs at birth and she had not had any treatments. As the policy stood, she should have been treated. We did not catch that baby was sick for about 24 hrs. When my shift came on, I was worried because he was 24 hrs and was not keeping his temp up at all. At almost 8 lbs, that should not have been a issue. And he was barely eating (mom was feeding formula so it was easy to see). When my shift called the doc - night shift calling at 9 pm on a weekend - we were worried. Long story short, the baby got very very sick and ended up staying with us for almost 3 weeks.
So, what I am trying to say is, do the protocol, watch for all those things listed by PP and also pay attention to baby's temperature and desire to eat. Being sleepy is normal but lethargic is not. And, most importantly, listen to your "gut." If you are worried that something is wrong, get it checked out asap - "don't wait and see" with a newborn baby.