Armorstands are dissapearing

I was in my survival world (Singleplayer). I made four armor stands and put them in my house. One of the armor stands had two enchanted pieces of armor, a diamond chestplate, and diamond boots. I went to do other stuff in the world and when I came back to my house, two armor stands had disappeared, one with no armor pieces and the one with the two armored pieces mentioned before.