I have a Red Rock that is just over 1yr old and has been laying for 8-9mos. When she first started laying, the eggs were normal. A couple of months ago, her shells got rough and thin with the occasional shell less egg. For the last month or so, she has not layed a normal egg. My other 4 hens are laying normal eggs. They get frequent egg shells, free access to oyster shells, they are pastured with free, daily access to sunshine. I have top dressed their feed with oyster shell. She is vigorous and otherwise acting normal. My water is not high in saline. I have searched the forums and read the link that many posted about shell less eggs. The only thing that seems to fit is the defective shell gland, but she did lay normal and thin shelled eggs for a while. I read one post about direct gullet feeding with a calcium supplement. Could it be that she isn't eating the calcium sources that I feed them? Does anyone have any other ideas?