Why do I use so much PH down?

I got a few hydro grows under my belt....this is the first DWC setup. 16 plants in one 4'x4' flood table. 45 gal reservoir...I use botanicare cns 17 with hydroplex. Ph keeps running up pretty quickly 5.5 to 6.5-7 in a few days. Is this normal?
Also, my ppm is rising without the addition of ph down. Shouldnt it be dropping? Plants appear healthy....slight nute burn from ppm rising. went from 840 to 960 in a few days, didnt add anything.
Using 1000watts, with plenty of ventilation....temps around 80 day and 70 night. Getting ready for the co2 as well.

Got any ideas?

If you ppm is rising, it means your plants are using water than nutrients..
Try running a weaker nute solution.

Clown Baby said:

If you ppm is rising, it means your plants are using water than nutrients..
Try running a weaker nute solution.

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Right on thanks again CB..ill give that a try. I got 10 gallons of water dechlorinating...ill add that to reservoir tomorrow. Drop it by about 200 or what?

not sure what your math is telling u but in a 55 gallon res I doa mix strenght for 24 gals. so i basicly do a 40 % strength

Tamorin said:

not sure what your math is telling u but in a 55 gallon res I doa mix strenght for 24 gals. so i basicly do a 40 % strength

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Not sure what your trying to tell me bro. What you mean?