Mob Glitch

I don't know how I triggered it, but certain animals are glitching and sometimes change. I don't really know how to explain this either. Sometimes the animals become invisible...What I did that possibly started(didn't always happen) I went pass the borders with chunks before it loaded, went back in, dug into a ravine, then built the portal to the nether. At first everything seemed fine. Even the Blazes looked fine. Then all of a sudden I came into the blaze I passed by earlier different, seen in the first photo. I decided to try with other mobs to try to see what else is affected. The pictures show what happend.