Ph and ppm change over time, is this ok?

Hey everyone, i have 55 gal res for my soil plants. i added all my nutrients (Roots organic line) and today around 3 the ph was 6.2 and the ppm was 910 which was exactly what i wanted because im just about to feed the girls. i come home around 8:15 and the ph is up to 7.1 and the ppm down to 780......is this ok? do i add more nutrients to lower the ph and raise the ppm again? or is this ok to feed the plants?

You suck, DONT WORRY i figured it out. For all the people who did view the post and are wondering the same. To my understanding, when using organic nutrients, over time the Ph will change. For instance if i mix up my 55gal res. the FINAL Ph after a a few ml of ph up is 6.1 and then over 24 hour period it shoots up a point or so.....this is ok, do NOT ph your water back to where it needs to be.