How soon before hatching do you hear the chicks peeping inside the shell? I have 2 Buff Orpingtons sitting on eggs that I ordered and put under them on 5/13. Tomorrow will be 21 days, but I don't hear any sound coming frome the eggs. I candled them about 10 after I got them and all but 1 looked fertile. I haven't candled them lately ,though. Should I give them a couple of extra days since the were "mail order"?