DWC Rust-Colored Roots!?

I'm having an issue with rust-colored roots in one DWC bin, also basically entire interior of the one bin is rusty looking. I'm not using any hydroton, so that can't be it, and I have 30 other bins going with almost exactly the same pH and EC with no problems.

sounds like a microorgansim

[bump]
The plants in this particular bin also aren't thriving so much as their neighbors upon further inspection (hard to tell which plant is which with the size of my ScrOG, 80 sq ft total), someone wanna let me know what's going on here? Three weeks into flower so it's grill time, gotta know what's the deal and what to do about it....

Sounds like brown slime. You need heisenburgs cure.