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 :)

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