i had this problem also and thought my birds were cracking their eggs and eating them....i waas wrong my hens were laying soft eggs...if you dont have any oyster shell you need to get some and mix it with their feed....i had a chicken who kept laying these eggs and they kept eating them but...
all ive gotten from them was that they thought it may have some old english game....i got these from a chicken breeder and she has all pure breed birds...but she didnt know the correct name for this breed she just called them brown bantys....i really think the female looks like the breed...
i have seen it happen when there were too many roosters and only a few hens....7 roos with 3 hens and they bred 1 so much that they killed it.....i wouldnt worry with that many hens but then again if they have just 1 that they all go for they could kill it also....as for keeping roosters...
it takes 21 days for the eggs to hatch so if she was only setting for 2 weeks it wasnt all the way formed and it didnt suffer at all....make sure to put water in the bottom of the incubator and keep the temp at as close to 99.5 as you can....it may go up and dow a degree or two and if it does...
i have a black sexlink rooster and he is a pretty good size....i have 4 hens with him and i have never seen him breed any of them....they all run from him as soon as he gets close to them usually....i have seen all of my other roosters breed hens except him....i know he is old enough to breed...