Are you birds young? I have three sets of hens of different ages, 1yr old, 1.5yr old and 2yr old. The 1yr old hens are laying just like yours, about 2 to 3 eggs a week. The 1.5 and 2yr old hens are laying 4 to 5 eggs a week. Also, I have not been able to hatch a single egg from the 1yr old hens. Only 1 out of 5 eggs is even fertile and they all quit early when incubating. The other hens have a 100 percent fertility rate and I have not had a single early quiter from them.
I don't know if it is the age or the breeding of the 1yr olds. I got my 1yr olds (two pullets and a cockerel) directly from Zook. My other hens are from Cubakid's line and are matched up with Zook roosters. All my cubas are being treated exactly the same, so I don't know if it is the age or something else.