Early Root Rot or Stain?

Being a DWC grower myself with over 30 seperate buckets i can tell you in my experience this is normal. Roots will tend to discolour overtime, Though if you add a nutrient rich reservior into the equation that can stain the roots but it does not harm them. You are highly unlikly to get root rot in a DWC system this is because the media or water is constantly reciving oxygen helping the plant uptake nutrients faster therefore there should always be movement in the water when doing DWC obviously I know people do use Kratky systems and have sucess but I wouldnt personally. another reason this can happen is not changing the reservoir water frequent enough. Personally I replace all the water in the pots every week when I can this is die to most weeks having seperate feed along with the fresh water they need. When growing in dwc plants can uptake nutrients very rapidly so its so important the water is at the right ph, tempture and PPM or EC or your going to run into problems I have had something similiar to this in some of my plants and it did not effect the plants growth or health what so ever. Anyway best of luck with the rest of the cycle you should be aiming for ph 5.8 temp 18-20c and a EC value of around 1 or higher depending on the size of the plants :) peace out bro and keep it green :) 👊 I will add a rise in ambeint tempture inside your grow area will raise the temp of your water so be sure to keep and eye on that it will not cause root rot but it will slow her down dramatically if she is not getting the correct water tempture it will also impact her ability to uptake nutrients. Overall water tempture ph and then feed that is the order you want to do it in your head but in practical you obv do the temp first then add nutrients and adjust ph at the end which is the easiest way I have found :) hope this helps i can only go from my own experience though so take non of this as scripture :)