It is pretty unusual for a hen to stop laying altogether in her second year and I would be suspicious that she might be internal laying, which is sadly a common problem in hens. I do not have Wyandottes myself, but I'm sure other owners will tell you that that this is unusual too. I would check her abdomen for any unusual swelling. Has her comb been red like your other hens or pale. If it is or has been nice and red, that tells you that she is ovulating. Unfortunately with internal laying, the hen releases eggs in the form of egg yolks from the ovary but they fail to travel into the oviduct and instead fall into the abdominal cavity, from which there is no escape. Over time, the mass of egg yolks builds up and forms a bulge between her legs and below her vent. It puts pressure on the internal organs like the heart and lungs and gut, often causing a constriction which means that poop becomes less well formed and butt feathers start to get soiled. Sometimes the fluid leaches out of the egg yolks and settles to the bottom of the bulge (ascites or water belly) and can be drained off with a needle, but short of major and quite risky surgery, the solidified yolks remain and eventually cause organ failure or an infection sets in (egg yolk peritonitis).
I hope your girl just ran out of eggs exceptionally early because internal laying will eventually become fatal, unless expensive hormonal implants are used to prevent ovulation.
Please report back if you get the chance to give her a thorough examination and compare to another hen of similar size. Internal layers often end up walking with a wide stance and sometimes quite upright like a penguin. They also feel unusually heavy when you pick them up.
Regards
Barbara
