Quote:It may not be important to find out which hen is responsible, just try some changes in diet and environment for all of them and see if it solves the problems:
1. Ensure adequate calcium in the diet: oyster shell free choice at all times. Try including some dairy (cottage cheese, plain natural yoghurt, milk) and finely crushed egg shells. Also try and cut back on treats for a week to ensure that they are eating enough of the commercially prepared layer's food, which should have pretty much all the calcium they need. If less treats equals better egg shells, you have your answer...
2. Minimise stress: excessive noise around the henhouse, or rough handling, or even a sudden loud thunderstorm, can cause them to lay softies. Try and keep the girls calm as much as possible.
3. As a final resort, if diet and environment don't help, you may find there is a disease process making the shells soft... common culprits are infectious bronchitis and infectious laryngotracheitis. Or you may have a hen with a vit D deficiency or a defective shell gland.
Go for the obvious stuff in points 1 and 2 first though. It's far more likely to be dietary or environmental.