Holy PPM Batman!

soil is tricky. if you are not noticing any issues I would not do anything. PH is on point, PPM meters detect how much current is travelling though something and most of the things in soil may not even be available to the plants but can pass a current. stick your ppm meter into a glass of sugar water. it will not move a whole lot despite there being many molecules dissolved in the millions. Add a dash of salt and it spikes. good conductor of electric currents. If your all ready growing in it, and there are no signs of over/under feeding then leave it, mix in some new soil around 30-50% and call it a day if your worried about reusing it. I have never measured my runoff from soil grows in terms of EC/PPM. I also do not water till there is runoff as it can water log the soil. now with all this said, it only applies to true soil not potting mixes. If you using a potting mix that is soilless its different. Good Luck!