Here’s those roots slightly color-corrected and enhanced a bit to get a clearer look at what we’re dealing with:
I made that second pic a bit too bright, and this is also important to point out:
That tip going dark like that (circled) can be a sign that they’re being attacked. There is a slight chance it’s still just a bit translucent, as some root tips can be, but I doubt that’s the case here as there are other signs of potential attack in other areas and not just on the tips.
In summary, it looks like a bit more than just nutrient stain to me. I’d say the symptoms up top are likely due to what you see down below. Hydroguard would be good as well as monitoring and/or reducing reservoir temperature if possible, unless you’ve measured the water temperature already and are certain it’s staying below 70°F all day.
You are catching it before it gets really bad, but if it’s not dealt with you will probably continue to see detriment up top. It’ll bounce back if it’s handled swiftly - add hydroguard and try to maintain cooler res temps in general.
It also wouldn’t hurt to rinse the roots off with h2o2 if you can (even the 6% pharmacy stuff, doesn’t take much), and then do a water change with hydroguard included. It’s usually recommended to rinse/clean out the reservoir (with the 50/50 water vineger mix) when this happens but you might be ok just adding hydroguard - really depends on how bad it was and how tough the bad bacteria is.