There is a dirty, black burn (especially one that deposits soot on a glass-encased candle)
This means things are not going to go well – the spell may not work, the blessing may fail, the person is in deeper stress or trouble than you first thought. There is a great deal of negativity around. Sometimes it is good to change the focus of the candle and ask that it be used to burn off the negativity, which will enable you to get a handle on the situation.