I am having much the same problem. My Arucana suddenly stopped laying and hasn't for a week now. I live near Seattle, and the days are rapidly getting longer. I have 6 chickens, and most days I get 4-6 eggs. One day I got 7??!! Lucy started laying when everyone else did, but abruptly stopped last week in the midst of a warm sunny snap here.
She's about a year old, and laid late last summer pretty regularly 3-4 eggs a week. She's not broody, not molting, food hasn't changed. She seems happy and in her regular place about 1/2 down the pecking order. She is pooping, and nothing seems "stuck". She eats her treats with everybody else, and I just don't know what's wrong. I don't artificially light them, and don't plan to. I had three that kept laying eggs all winter anyway.
They free range the backyard, there's only two places she could "hide" eggs, and both are empty. Wouldn't she be broody and sitting on them if she was? She's always out with the flock, vacuuming up bugs and grass whenever I look outside.
Thanks for any advice.