I clean my res nearly every week. I also run an aquarium Chiller to keep nutrients temp between 64-72F as temperatures get over 100F here.
My ppms are staying the same.
My tap water has recently dropped from 7.0 Ph to 6.7Ph.
In total this week I have added 9ml Ph UP just to keep my Ph level at 5.8.
I appreciate the advice and will keep an eye on readings and see how things unfold.