Both plants developed root rot right after i changed nutrient solution. Luckily was able catch in time. Noticed plants wasnt growing as fast and sure enough both plants had sum rot going on. Plant "B" was worst i had to trim sum infected roots and gave bath in hydrogen peroxide solution for about an hour and got remaning roots back to white looking good. Plant "A" i didnt have trim any roots but did have to soak in another peroxide bath. While i cleaned entire system thoroughly. Air stone in plant "A" was extremely dirty. So i replaced. Both systems getting little better air flow now. Added sum peroxide to nutrient solution of both plants. Hope that helps them to recover. Unfortantly its not looking good for them.