I've gotten root rot, and it's best not to add anything. Especially Hydrogen peroxide or bacteria like hydroguard/aquashield/great white. Its usually the watering/drainage that causes it.
I recommend watering away from the stem and more at the roots. Make sure if you have rapid starter seed...
I forgot to drain the rockwool cubes after the 5.5 PH pre soak so I'm pretty confident on the over watering. It says rockwool should contain 20%-40% water weight. My cubes were saturated to 100%.
I squeezed out the additional water and I will update if they recover.
I was using heavy nutes on both, so i'm assuming over fertilization locked out some nutrients.
I water heavy once in the morning. This could also be it since rockwool cubes can sit a couple days without water
Same technique as this one and clearly she's better