Roots turning brown with every water change

Hello. I have been having this problem ever since I started growing in my DWC system. Every time I do a water change, my roots seem to exhibit root rot. The water temps are fine PH is 6.5, I have 1 water stone per plant (2 of them) and I am using a 10 gallon DWC. It seems to go away after a couple days but still stuns my plants growth and destroys most of its roots. I even bought aqua shield to see if it would help this time around. I want to know if anyone has a solution or a reason that this would happen.

Thank you!

Your method of growing is considered hydro isn't it? So you want a 5.6-6.0 ph?
How often you watering and is your water real wet?

I bought the marijuana horticultural bible one by Jorge Cervantes. And in the book it recommends PH between 5.8 and 6.8. I have a nutrient solution that adjust it automatically to 6.5. And I don't know how to answer the last two questions. I dont know if they were legit or not .

MrGhettoGrower said:

For dirts and soils you wanna ph of 6.3-6.5 but for hydro you wanna ph of 5.6-5.8 this could your problem~

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So what you are telling me is the book is wrong?

I have two different books and they both recommend 5.6 to 6.0 for hydro.

I roll @5.85-5.95, anything out of those tolerances and it is time for me to adjust.

Lol everybody is getting f$kd by this Cervantes Guy. start with 5.5 and when it gets to 5.8-6 adjust. That's it. Oh also buy some Hygroenzyme it will work wonders cleaning up your roots.. although if it's getting serious, use 5ml of H2o2 per gallon of water, leave them in that solution for 24 hours.