Howdy lonnielmb72, it certainly does look like root rot to me. I keep the root rot under check by first; ample aeration of the reservoir, I use a four outlet air pump with four 4 inch air stones in a ten gallon reservoir. Secondly; I keep the water temperature below 70° F by using 0.7 L ice bottles (changed out as necessary). Thirdly; I use aluminum foil and duct tape to completely block out as much light as possible from leaking into the reservoirs, I even cover over the Hydrotron pebbles in the net pots. Fourthly; I use 2 ml of GH FloraShield per gallon of water as an inoculant. You can give a large dose of hydrogen peroxide to the reservoir to shock the root rot, but do not use it if You are using a 'live' bacterial control, such as Hydroguard or similar, as the H2O2 will kill it as well. I have tried the Hydroguard and a couple of other root treatments, but they did not work as well as just keeping the stuff from starting in the first place.
Try to clean the reservoir out by first treating it with the H2O2 and then flush and rinse as much out as possible, then start with fresh nutrients.