Before I updated minecraft from 1.6.1 to 1.7.0, my world was fine with no issues. But after upgrading my game to 1.7.0 update, some blocks, when I point at them, becomes black in color (mainly Quartz blocks). I also shows some black lines. I had this world for more than three months, but suddenly, this issue occurred. It also appears to other players playing in this world. I neither use any resource packs nor behavior packs. I think there is a problem from directly upgrading my game from 1.6.1 to 1.7.0.