RUN OFF PPM is INSANELY HIGH

so i've been having some browning,curling,drying issues during flowering and i kept concluding this to be a P or K and cal/mag deficiency .

i am growing in rockwool cubes and soil .

if the PPM of my runoff water is 3000+ . . wtf is going on ... not to mention the ph is about 4.5-5 . most likely due to the high PPM . i have been giving them ph balanced solutions at about 5.8-6.0

i'm guessing it's an over-fertilization problem but what can i do to fix this problem besides a flush ?

i hate flushing . it seems to be so stressing on the plants .

THANK YOU RIU IN ADVANCE

also . what medium has the easiest ph to keep stable ?

i'm using FF nutes combined with some Roots supplements

Just tested my runoff and my ppm's were even higher than yours, so I would love to get someone with a bit more experience to respond. I am also in soil.