Diagnosis my plant! Root or stained?

I noticed the pH swing when I changed the res last. I hadn’t before but I checked it last time and it was sitting at 8. So I’m premixed the nuits last night and will be readjusting it accordingly. I’ll order a larger bucket today. I noticed it was using quite abit of water and read somewhere that you’re meant to gradually drop the water levels to encourage the roots to stretch more. Is that correct?

You can use sensizyme with your grow to eat any unwanted crap in the root zone. Works like a charm as long as water temps stay below 70f. I think 21c is about same. I use 5ml per gallon if there is slime on roots. If no slime I use 2ml per gal.
Make sure air stone is clean and air pump creates a rolling boil look to the water. Low amounts of air will cause drowning symptoms like droopy leaves or 8t can cause root rot
And keep water level 2 inch below bottom of net pot.

And dont be shy, touch the brown and see if its slimy.

So I reinstated the nuits. Here’s some pics of the roots. No improvement on the leaves. It may actually be spreading I think.

Net pot should be 1 1/2 to 2" above reservoir level. If not will cause damping off issues. Which further reduces bucket rez. Make sure there’s plenty of air so rez looks like a rolling boil. Droplets will be flung up to the net pot as well, keeping it wet at the bottom.