This is a very strong possibility. Sex change generally associated with ovarian problems/tumors sometimes occurs in chickens. I have seen it once in a RIR hen who around 4 or 5 years of age became masculine during a molt and developed roosterish hackle, saddle and tail feathers. She also grew spurs but never crowed. Something that I had read about but never witnessed until this occured.Yes pictures would help but it sounds like your bird has gone through a hormonal sex change.