Horse duplication

I was playing a couple days ago and when i got off my creative world i was riding my horse which had a name from a name tag and was wearing diamond horse armour. When i got on to the world today i looked around and saw another horse that looked like mine and had diamond armour on. I never put diamond armour on any horse other than the one i was riding and when i looked directly at it its name was my horse's name. i hopped off the one i was riding and both were the same with the same horse stats aswell. both could jump four blocks and i relised the horse got duped