Invisible fire destroying custom maps

When I go into one of my custom maps there's little black specs like the torches and fire give off then I lose hearth and everything is disappearing it started to happen when I updated it to 0.7.0 I think there's "invisible" fire destroying my custom maps plz help but it doesn't do it to my normal worlds I made in mcpe only ones I downloaded but I didn't even do any thing to the world with flint and steal plz help thanks