Could be your juice, some of my older coil builds get bit of rust on them but nothing a bit of dry burning/water can't fix. I've also heard brass/copper does something to your juice/wicks that makes them turn funky colors. One of the main reasons I've avoided full brass/copper RDA's though I may be wrong.Might be nothing, bought a brass Goon about one week ago. Noticed my coils had a rust color and cotton was also discolored but nothing that bad. Was time for a coil cleaning and re-wick today, cotton was a lot worst so I am now concerned. Anyone else having this issue?