I am a new homeowner and have a concern about some cracks I have seen in our bricks. We have a split foyer home so the top half of the house is siding and the bottom half is brick. I have noticed that several bricks have a small hairline crack down the middle. The crack is only in an individual brick and does not extend into the mortar or into another brick. There is no pattern at all and its only random bricks that have this. Do you guys know if this is normal or something to be concerned about?