What went wrong?
The next time you caught a glimpse of your lovely, healthy candle, you saw a clear crack running straight down the center of the candle top.
When quickly cooled, larger-diameter beeswax candles may occasionally develop a crack as the wax pool hardens because beeswax shrinks as it cools.
This is merely a consequence of burning beeswax, not a defect with the candle.
Try to gradually chill your candle in a warm part of your home to prevent cracks, but if they do occur, don't be disheartened!
It is unlikely to have an effect on the candle's performance and will almost always fill in once the light is lit again.
After relighting, tilting the candle sideways might be a good idea if the crack is extremely deep in order to try melting wax from the area around the crack to fill it.