Sorry Jash......I misread the numbers completely. Yep, that's your ppms dropping all right so they are indeed eating things......how often are you changing out your res and making sure that the nute ratios are staying pretty correct? If it's more than once a week then I'd raise nute numbers......that's some pretty PIGGY plants.

How about flushing your res and medium? I used to have a LOT of problems with nute/salt buildup in my medium and would have to flush often to keep the roots happy.

Are you using anything for root health.....Cannazym or even H202?