Tooth turning grey for no possible reason with no pain or sensitivity. Any suggestions? (photos)

Hi , As I'm in the process of cosmetic dental work I noticed that one of my teeth is turning grey. I noticed this after we bleached the teeth and did a gum lift procedure . there is also a gum lesion beside the tooth which I thought was because of the gum lift but it's been a week and it's not going away. I also don't have any problems with this tooth, it's nerve is working but it's not sensitive it also doesn't feel like it's decaying.