Chicken has bare spots on belly and breast, a LAYING
Just listing more symptoms.
The least i would do is put some vitamin supplements in their water, give oyster shell as an optional supplement. Its maybe that is going broody - i have two hens that lay, but stay on the nest afterwards (until i remove them from the nest). When hens go broody they do not eat and drink as much as usual, leading to a lack of overall condition.
Sorry i cannot be of any more use.
But that is under control.
Thank you for all your help.