New extension to bungalow 7.5m x6 m and new double garage 6mx6m. Issue is that some of the face blocks are cracking in the middle on both builds and some cement lines have come away from the edges. It's like the blocks have shrunk. The 7.5m gable does not have an issue used blocks from old garage after cleaning them up as gable not seen from road. Only new blocks have this issue. Any ideas? The blocks were purchased from a well known merchant.