Both of those are still within normal limits, so I honestly wouldn't worry about it at this point unless you have several hard corals in your tank that are starting to eat up the kH. For now I'd start testing your alk and calcium once a week and see how stable it is over the course of the two weeks between water changes - if it stays between 7-8 you should be just fine, if you notice that it starts to drop towards the end of the second week before you do your water change, then you can consider dosing (but will want to check your calcium as well to know whether you need to dose one or both).
For pH, you are also in an acceptable range, but if you are concerned about it you can try running the light on your 'fuge 24/7 (you might already being doing this, I'm trying to recall from your other threads). pH tends to be highest at the end of the day after the lights have been on for awhile. If you find your pH dropping below 7.7 then I'd look into adding a buffer, but as long as you are at 7.9 you are just fine!