I would bet that the white powder you saw at the bottom of the container was nutrient salts built up. If you have 30% perlite, flushing should not cause it to soak permanently. I stand by my
Flushing recommendation, and if you are scared take a shop vac to the bottom of the container to suck some excess water out.
I once overfertilzed and burnt a plant very badly, it took a month and a half to get it back to normal.
How did I know it was too much nutrients? I tested the PPM of the runoff. It was over 4000ppm. I recommend you do the same with a TDS meter. That will tell you how much nutrients you have added.