candle issues

I’ve looked just about everywhere for why this might be happening and I cannot for the life of me find an answer. Please help !! So, I’ve been having a weird issue with my candles. I just started making them a couple months ago and I’ve only just now started actually burning the “successful”...

I've noticed this happening with my scented soy candles. They look perfect initially but after a few weeks this weird ring seems to appear around the edge of the candles. Does anyone know why that is or how to prevent it from happening?