those brown roots are possibly showing rot, go ahead and run a H2O2 dose with your hydro solution ... I would add hydrogen peroxide, and let it run thru your system for a couple days, along with your nutrients, or with plain water ... keep in mind the peroxide will also kill off the beneficial bacteria, along with the bad ... so, after treatment, flush well, and add some Fox Farm Grow Big, or similar bacteria culture additive, to replace the missing organisms ... lay off the nutrients, until the plant perks up ... I wish I could give you a dosage on the peroxide, but I usually just tossed in a quart bottle, per couple gallon container of water ... not very scientific, I know :wtf: