Rust looking stuff on roots....what is it?

Over 24 hours I started to notice a growth in my roots that looks like rust. I use gh 3 part and heis tea.
Anybody dealt with this one?

On my roots... Sorry.
It rubs off. It's not slimy. No smell. No clue

probably just nute residue. roots are good filters

I think it's alive... I cut a piece of rusted root (hehe) off and dropped it in a h202 mix (3ml of 29%)
I could tell after a few minutes it was fizzing from
The rust.