As long as your mistake is a learning experience and doesn't happen again then there's nothing to feel stupid about. I have a pretty long list of boo-boos myself.
Should get as much of the damaged roots out as you can and dose heavily with peroxide for a while to kill the bad shit off or it will be back. I used 35% food grade with my DWCs.
Any idea what your nute temps are? 65 - 68F is best to prevent rot and once I made a DIY chiller out of a water cooler I never needed peroxide in the tubs again.