The chicks will usually pip closer to the middle of the egg because of the position their head is in when they are folded up inside the egg. It is perfectly normal, and they do not need any help to zip and hatch. Do not open the incubator because loss of humidity does cause chicks to die after pipping, and trying to help them out of the egg could cause bleeding and other problems with the yolk not being absorbed totally and could cause the chicks to die also.
If this is your first time incubating and hatching it is so exciting and you want them to all be fluffy and chirping and you think you're helping them hatch but sit on your hands! - be patient and they will hatch just fine on their own. Good luck!