Remembrance Garden at Church

The idea of this was to Buy a Brick to raise funds for a New Roof. A tad expensive for a house brick and  my family already have Headstones. However its a nice idea so I bought 4 and I can sit in Church without putting an umbrella over my head as the roof no longer leaks. My four are below the circle on the unclear photo. It was raining yesterday but I am puzzled as to why the engraved bricks are dark and wet and the others aren't ?