ppm use by the plant

[sadhu9]

I have wondered when I feed my plants a certain ppm nutrient solution, should that specific ppm number (let's say 900 ppm) decrease every day or stay the same? I change my nutrient solution every seven days and usually the ppm will decrease slightly every day. But sometimes the reading will stay the same or fairly close to it. That is the problem I am having with two plants that are flowering. I grow with DWC...
Any wisdom on this subject?

Sadhu9

 

[CO Finest]

It should stay close. When plants take more nutes then water ppm lower, when plants take more water then nutes then ppm higher,when number stays close then plant taking both equal.

 

[sadhu9]

OK,but when ppm rise, is there a problem with nutrient uptake to the plant? If the plant is using water and the ppm rises, is this normal?
Can this cause a nutrient lock for the plant?

Thanks,

Sadhu9