I like to burn tealight candles as a way to get myself in the mood for witchy work and as a form of every day devotion. Lately, I have been noticing a purple streak along part of the edge of the tealight candles as they are burned down. For example, if I have to leave to go to the grocery store, I snuff the tealight out (and the wax is perfectly clean, nothing gets into it), but when I come home there is a line around part of the edge that is now purple. Is this a common thing with tealight candles? Or could this be an indication of something else?