another ppm question ???

Trying to figure out how my ppm's keep are getting up to 1500 ??, 2 weeks into flowering, i had to flush last week had leaves dropping like flies cause my ppm's were up to 1900, so im still semi flushing with pure h20 with a base reading on ppm's @200 after i adjust the ph to 5.6.. Im under a 400 watt hps, good ventilation, both plants about 2 1/2 ft tall and very full. Living in an aerogarden 1 gal. Resevoir. Im trying to get to add bloom nutes but dont want to have toxic ppm levels,, any suggestions ???

What kind of water are you running? Try running distilled water if your ppm is too high from your tap water or whatever your using. Are you adding nutrients? If so your definitely adding too much man but that is obvious so you should know that... you could have heavy salt buildup but that should be visible white residue.
What are you using to check you PPM? Have you calibrated it recently?