Heres a tip. Empty that cesspool and spray off all the roots good. Take a garden hose sprayer or sink faucet sprayer and spray from the top of the pots and flush a ton of water in there. Clean out the reservoir good, real good with scolding hot water and dawn dish soap. Soak those air stones in 1:5 bleach to water ratio for a few hours with them bubbling. Soak that air tubing as well.
DO THIS FIRST: Go to the store, buy some earth worm castings, some hydroguard and some mycos product. Take a ladies stocking (i use a few) and stuff a handful of earthworm castings in it. Put a smidgeon of mycos with 8ml hydroguard per gallon of DISTILLED water.
I use two gallons or distilled water and double everything I said aside form the ladies stockings, those are just a filter so the castings dont get in there.
Use an air stone to bubble the mixture. I put the stocking filled with EWC on the air stone. Lastly give it some sugars, a popular product is molasses in which you want to just put a teaspoon of it in per gallon.
Bubble this for a few days until you get an earthy smell like mushrooms and some slight foam. This is good.
it is important you use distilled water as the bleach/chloramine in most household taps will kill your beneficials you're trying to breed.
So after this is brewed, put it thru a coffee filter to get any residuals and strain it into a gallon jug and refrigerate. Good for a week in there unless it starts smelling bad. And by bad I mean anything that doesn't smell like mushrooms/dirt.
Pour a cup of this stuff over the top of the pots and let it trickle into the res. Do this once a day for a week.
Don't look to the rotted roots for improvement. They won't improve.
Then use the hydroguard you purchased 2ml/gal every few days apply some.
I usually put 6ml into a half gallons worth of water that im using to top up my res and pour it over the medium and drench the roots.
Hope this helps