Final Chicken Update

Well, I am sad to report that after weeks of waiting there are no chicks. On Thursday, day 21, there were 4 eggs under the hen. Thursday afternoon I found, outside the nest, a dead, wet, cold, chick. All day Friday she wouldn't let me near her. And then on Saturday morning I found another cold, wet chick outside the nest, still covered in bits of yolk and shell, so I tried to have a go at reviving here, and brought her in the house and put her in a box on top of the boiler but she didn't come back to life. And then when I went back into the barn to look at the broody she had got off the nest -- and there was nothing in there! So I have no idea what happened to the other two eggs/chicks... I have now put her back with the rest of the hens and she is not acting broody anymore... So no chicks for now until the next hen decides she wants to have a go. Anybody have any idea what went wrong here? Was she just a bad Mommy or was there something else wrong?