I have recently started a new world on PE and was strip mining for diamonds at y = 11. I found that some stone blocks took longer to break and a silverfish spawned from it. And it just died after 2-3 secs on its own. This happened quite a few times (about 4-5). I think silverfish generally spawns in the stronghold. Could this be a sign that I dug under the stronghold or is it some bug or feature that I don't know of.
P.S. - I don't have a screenshot atm, but will try to mine in that general area to find some more blocks like that and gather evidence. S