1st hydro grow... ppm increasing...

Hello all... I'm currently doing my first hydro grow in a bcnl grow cab... I have a 14 gal rez which I change the nutes in every week according to the an calculator... I check all my vital signs daily ie: ph, air temp, rez temp, ppm etc...
My ppm is rising daily and by the last day of the week the ppm is already above what it should be for next weeks nute schedule, up until now I have ignored this b/c everything looked great but I have been noticing some yellow spots in the leaves and think this could be due to this issue... Is it possible that due to evaporation of the h2o in the rez that why my ppm is increasing?? Should I just add a gal or two of ph'd water halfway through the week to deal with this problem... Any help would be much appreciated... Thanks
Jim

yeah man. if your water levels are dropping, your nute concentration is going to rise. keep the water level the same and your ec should remain fairly constant.

rite on, i appreciate it... thts what I figured, its looking badass tho, getting real excited starting wk 4 flower tomorrow and its gna be sum dank ass ak47!!

my ec has been going down the bigger they get cuz they are using the nutes but i also have my ec at 600 which i think means my ppm is 300 whis is low but they are seedling soon as their bigger do you know what it should be?

i think you may be confused on ec... ec should be around like 1.8 to 2 u which translates into roughly 1400ppm for 2.0 ec, but I do think 600ppm seems about right for vegetative plants... maybe a little high for very young seedlings... I am also probably not the most knowledgable person on this subject but I do know ec is around 1-2... do you have a gd meter, apparently so...