Plants not eating

I have an aeroponics under the UFO LED and it seems my plants are not eating. I am using the receipe for success and in week 3 of veg and my EC/PPM reading is stay about the same and sometimes rises (700ppm). My ph seems to go down. I started the first 3 weeks using only 1/4 the nutes that the receipe says and my resivoir has 10 gallons of water. I am using the hydroten balls and noticed a white mildew on the cups and balls so i thought maybe i had a salt buildup. i then purchased some clearex and flushed my entire system and still the same result. The good part is my plants are growing and roots look good but just dont know why these numbers are not going down as if the plants are eating. is there a special process to cleanse my roots if they have salt buildup? sorry for the ramble but your advice is appreciated.