Coil turning brown/black 1 day old

I've been vaping out of my new coil today and I noticed my coil is turning brown in 1 day! The flavor is tasting metallic and I make sure everything is full and don't chain vape is it possible to get a faulty coil? (pre-built coil) I also did prime it and even left it for 10 mins to fully soak.
Any help much appreciated hope everyone has a good weekend :)

Original source: https://www.e-cigarette-forum.com/threads/coil-turning-brown-black-1-day-old.959131/