I've had a similar issue, and found a thread on another board on the topic. The solution for my system was to use a magnesium anode to help with this. People reported that the rust would go away when they mounted one in their kettle. It is basically just a metal rod that you attach in your kettle near the heating element. It requires another hole in your kettle to mount, but it is a full-time mount that you don't need to mess with once in place. The anode I got off amazon was for use in portable hot water heaters (like on an rv or house boat). Total fix is less than $15 for the few parts needed.