Too much N was correct, but 'flushing' no. You had some 'clawing' from N but that is irreversible anyhow.
Next time just adjust you npk so you use half the N for a watering and go from there.
If the 1 or 2 part fertilizer doesn't allow that, just cut back to 2/3rds strength with runoff.
But I also think you medium holds to much water/not enough air to begin with.