When they are real young like they are now I might do a 2 week run since right now they are building a root system so they are not going to take in allot of nutes and such. They get a little bit bigger and switch to full str on nutes then it would change for me to every week since you dont know for sure exactly what they are feeding on mostly or how much. Yup you can take a pen and check your PPM's but what are you low on?? My case would be either Micro, Grow, Bloom, calmag, florious plus or in flower KoolBloom. To my knowledge there is no way to tell if they are feeding evenly across the board or if they are using all the grow but none of the bloom. Weekly rez change will help eliminate the guess work as you start fresh every 7 days :thumbsup: