Brown is not bad in it's own right. Are the brown roots firm, or are they squishy. Firm means they are still good and probably just stained brown my the medium.
I think they look mostly OK, I'm not sure about the center of that last picture. I've seen ones similar but just cannot remember if I've ever seen it on ones that were healthy or ones I was having probelms with

hopefually someone else can comment on that.