Are your roots or stems rotting beneath your rockwool? Are you using full strength nutrient concentration for your cuttings? Is your Rockwool sitting in nutrient, or what is your cloning system?
I have had root rot with some of my clones when my nutrient strength was too strong or the oxygen concentration was inadequate. I have also found that certain plants respond better to different nutrient concentrations. For example, I can not use any nutrient  just aerated water with salvia apiana. I can use a very weak nutrient solution with papaya, confederate rose & paw paw, & any strength with native ephedra & Mexican salvia.
I have found that different systems work better for different cuttings. I have a simple system with only a waterfall pump & an aeroponic system. The waterfall system works better for salvia apiana, & the papaya roots rot if not given extra oxygen. I have also found that if the root is rotting I may be able to save a clone by cutting off the bottom & trying again.
The peroxide may help, but not if your roots have rotted.