Are the chicks inside still peeping and talking? If they sound lively, they are likely fine. Its when they begin to quiet down that means they are weakening.
If your worried, just pick a bit of the shell away so that the chick is getting more oxygen and so you can see what is happening. If this doesn't help them then you may have to assist the hatch. Be patient, some chicks take a while to hatch compared to others and helping too early can make them bleed (eggs tend to bleed when helped, but the more they bleed the less likely they are to survive the first day).
I hope this helps and I hope they all hatch healthy!