That they have plenty of nutes and are drinking up more water than nutes.....that is normal and usually why they recommend topping off at 1/4 strength nute solutions and such....to help readjust the balance. Keep in mind though that your ppm number does not reflect percentages....ie...did they eat all the phosphorus and leave the potassium behind....only total ppms. Does that make sense?

When I had deficiencies after I switched to bloom nutes my ppms would drop....fairly dramatically about 200 a day....that's when I was informed by my hydro guy that my plants were....ahem...."pigs" and to definitely up the nutes.