I am at day 21 with my eggs and a number of them have started to pip and I can see a small crack on the outside of the shell but the chick has not gotten through the membrane. Is this normal or do I need to make a hole in the membrane?
I'd guess that what you're describing is normal. A pip at first looks like just a tiny crack on the outside - and will stay that way sometimes for several hours before the chick starts to hatch. It is actually through the membrane, but may not look that way. To have cracked the shell at all it had to get through the membrane.
My advice is to leave them alone! Don't open the door and, if you can stand it, stop even looking in the incubator! LOL You'll drive yourself crazy and will probably end up doing more harm than good.