I assume you are speaking of run off
Take it somewhere you can drain gallons (bathtub or shower)
Run gallons of pHd water thru until you’re below 1.0 EC (500 ppm) and then feed with usual feed.
This is assuming you’re feeding bottled nutrients and not some amended coco type set up.
This happened to me occasionally for different reasons. What I’d usually do to save water is saturate the medium for a few minutes let it sit, this makes salts soluble again - then flush as instructed above. Rather than just flushing non stop.