What day are they on? You said they were due to hatch on the 27th. Are you considering day 55 the hatch date, day 60 or another day? Without knowing how far they are along I cant really give advise if you should cut or not.

Of the other hand, have you cut eggs before? If not are you 100% comfortable with the idea? If the answer is no to both questions your best option is to let them pip on their own.