Roots Turning brown please help n not just view

[Kushmaster216]

Does anyone know the reason my roots keep turning brown I don't understand what the hell I'm doing wrong so any info would be nice please n don't just view to not say anything this post are suppose to help people n I don't seen many people Tryna help us new grower out so please help me out thanks

B.c. Nutes but I'm not giving max strength.
Ph around 5.5to 6.7
I do not know the ppm I'm running tap someone told me that's around 300 ppm
2 air stones
Og kush clone
Deep water culture
Res temp 67to around 76 at high test but it hardly reaches that
Closet temp 73 to around 80
600 watt hps
12/12 light cycle
Closet dims length:6ft2in width:3ft6in height:7ft8in
1 30 gal pump 1 15 gal pump
Please help out guys I'm Tryna get big yeild I feel like my griw closet has potential to grow decent size plants I'm only growing 3 or 4 at a time tho I only have 2 going now but I would like to get started with more soon I have a veg space in my dresser letting plant get about 1ft and a half before flowering

 

[Kushmaster216]

Here r the pics

 

[SWvoodoo]

Light. I believe that those two buckets would not be light proof and I mean you need it black as black. No light. Nada. BLACK. Get some foil and wrap those buckets. You may have to cover your medium aswell depending on depth etc (I like to cover my medium to prevent algae buildup on my rockwool). Even your clear air tubes look like light sabres in a truly dark reservoir , I tape those off to prevent any light as well.
Do you use organic nutes or beneficial bacteria? If NOT dose them with 3% hydrogen peroxide @ 2ml/L and do that with every water change. No more root rot.
Fix the cause of the problem by keeping temps low (higher dissolvable oxygen) and no light (algae needs light to live).
If temps get over 70f or so add a ice block to your reservoir to help ease the temps.
I am by no means a professional but this is what I did and it worked.

 

[waknbak88]

SWvoodoo covered everything I was thinking as I read your post. good luck man

 

[shaggyballs]

pythium maybe