Here are the roots of Cyperus helferi. Notice the brown, thin, and heavily branched roots. These are the symptoms of toxicity. Healthy roots should be thick, white, with noticeable root hairs (the fuzz) as is seen growing after the plants were removed from the substrate and placed floating in a separate tank. Roots should never be brown.
Classical Aquascaping 
Just received some C. Helferi whose roots look just like this. How do I get the plants to recover?
LikeLike
When I got my C. helferi in the agar gel packs, it also had brown roots due to being grown in the nutrient medium. Just make sure that the water it’s being grown in doesn’t contain toxic concentrations of heavy metals and the roots will grow out healthily. RO/DI, distilled, or rainwater that is remineralized will usually be better than tap water.
LikeLike