The torches cast light to certain blocks only. I am actually not sure, but I think that they are near the edge of a chunk and they (for some weird reason) aren't casting light to the other chunk. Anyway, the fix to this is exiting the world, then reentering. It occurs in both beta and in ordinary bedrock edition on my phone. I have some screenshots of the torches casting light normally and some of them lighting my mine shack in a rather peculiar way: