dark area on roots getting larger

So this is getting a little concerning to me. its happened before and did not end well. noticeable browning started about 3 days ago and seems to now be growing about an inch per day. These are 2 weeks and 5 days into veg, and suffered no stress with transferring from the cloner. The canopy is very healthy and still growing vigorously without symptoms.. so far... The roots are still growing rapidly and for the majority are white and fluffy. Im suspecting root rot or an infection but unclear as to the cause. As you can see I did pull down the roots from the top to make sure water wasn't pooling.



A little more info..
There are a total of 8x 5.5lph nozzles, 4 on each head rotating at 50rpm during spray.
They spray for 0.4 sec every 4 min... so that adds up to about 5ml total per cycle in a chamber that is 4ftx8ftx2ft. where's atomizer when you need him?!
pressure ranges from 70-90psi via an acc. tank, figured slight variance in micron might play in my favor.
Nut. temp is 68-70 deg. and the chamber temp is consistently maintained at 69 deg.
RO water with Canna full line nuts.+ hydroguard, calmag., and silica. ph 5.7 - 6, ppm slowly inc. to 1200.
As you can see in the pic. the roots rest on a silk screen that water is able to drain through.
I know it looks like some run off from the pex could be the corporate, but the pex is actually positioned above the opposite side of the decline.

So far ive propped the screen up under the browning area to promote more drainage.. dropped my spray time down to 0.2 sec.. and inc. to the rec. dosage of hydroguard.. I'm now convinced that h2o2 is not appropriate.. the canopy still looks great. im ready to flower but would rather get this cleared up first!

Any ideas or recommendations? Is there a way to spot treat an area of roots, or should I just cut the whole area out!? Im still fairly new to growing and would really appreciate some more experienced grower's input.

I'm sure you will get a few different suggestions which is great, meaning there has been success in a couple different approaches. It definitely looks like beginning stages of root rot to me. Looking at your pics, personally I would cut out the brown roots from the one on the right because they won't 'come back' just take up space, and the pythium is in there pretty good. The rest of them look great. Do you have the ability to lower your water temps to mid 60's as well? I believe that would also help a lot. I started in sterile, had an issue about the same time as you, and switched to hydroguard, although i'm in rdwc. You have to kill all the bad bacteria with say h2o2 first, then introduce the hydroguard after the h2o2 has evaporated or else it will kill the hydroguard. I think of hydroguard more as a preventative than a solution. It keeps pythium at bay by consuming it's food source so it can't grow. If it's already prevalent in your system, hydroguard will have a harder time defeating it. Wipe out the battlefield then introduce your army so the enemy can never grow.

Thanks for the reply.. seems like for now it hasn't moved far enough to get to the other plant yet.. can I cut everything away but leave the tap roots intact? I have 35% h2o2.. I would normally mix 4ml to 1 gall ro, not ph adjusted, and run for 3 hrs. Sound ok?

I run a constant 1-2ppm sodium hypochlorite. When combined with dtw, nasties have a hard time getting a foothold anywhere in the system. Recirculated nutes and just a periodical blitz with h2o2 will give them more of a chance. The buggers are always lurking, looking for an opportunity to strike I`d cut out the iffy roots and disinfect that area of screen. If you tilt the nozzles at an angle you could oscillate the mist up/down as they rotate.

Atomizer said:

I run a constant 1-2ppm sodium hypochlorite. When combined with dtw, nasties have a hard time getting a foothold anywhere in the system. Recirculated nutes and just a periodical blitz with h2o2 will give them more of a chance. The buggers are always lurking, looking for an opportunity to strike I`d cut out the iffy roots and disinfect that area of screen. If you tilt the nozzles at an angle you could oscillate the mist up/down as they rotate.

Click to expand...

How do u make the sodium mix, how much do you add. I purchased some. Sodium hydrochloride and I'm a little unsure how to mix and amounts.

Check the label for the sodium hypochlorite %, you`ll need the concentration to figure out the dilution rate.