I have a flock of 4 RIR hens. I started with 4 hens and 2 rooster, but I got rid of the roosters due to my hens being ravaged.
A year or more ago, one of my hens stopped laying. Before she stopped, she was laying on the grass and in weird places, and they were pretty thin shelled eggs. Then, she stopped. She was limping for a while, then lost a lot of weight, but she is better now. During her winter moult, her feathers grew back in a variety of different colors. While once she was just the typical RIR brown, now she has black, white, and greenish shiny feathers speckled all over her brown plumage. She still won't lay. She has always been a very aggressive hen.
Recently, one of my other hens stopped laying. She used to lay every single day, despite being the bottom of the pecking order. Before her winter moult, she had an egg stuck that I assisted her with laying. It was big, but she laid after that with no problem. After her moult, she laid probably for about 3 weeks before she stopped again. Her butt is all poopy and her butt region feels a little too big in comparison to her sisters. It doesn't feel abnormally hard or soft, just big. It isn't red either. She used to be a really sweet hen, but a few months before her moult, she started acting almost as aggressive as the other hen that stopped laying. This makes me afraid that she also will not lay again like the other hen.
Some background info:
They are all 2 years old.
They have a large pen (about 500 sq ft) where they are able to forage for grass and weeds.
I feed them layer feed, provide oyster shells, and they always have water.
They all moulted for 6 months, and did not lay a single egg during that period.
I live in Hawaii, and the hens went through a winter where the day length only goes down to 11 hours.
The lowest the temperature got was 59 degrees F.
They have access to areas with sunlight throughout the day. They also have plenty of shade.
We have had issues with mongeese steeling their eggs. This might be a stresser.
They do get treats on occasion, and the week that the second one stopped laying, I was giving them lots of treats.