Those are hens - like EmbertheChicken said, one will sometimes decide to crow and act like a rooster. They don't actually change into males, but they start to display secondary sex characteristics like crowing, feathering like a male, dominant behaviour and no more eggs. I've read that illness or an injury to their ovaries sometimes can cause it. It happened to one of my Rhode Island Reds "Rooster", who had recovered from an earlier unidentified illness (vomiting water, sitting in the corner and not moving), but after we got a real rooster, "Rooster" starting laying again and behaving like a hen.