pH will fluctuate through the course of the day. my pH is the highest at about 7pm and the lowest at 8am. so, depending on the time of day, you can get different readings. also, gas exchange will increase pH. if you have a flat water surface, it leaves no ability for co2 to be replaced with o2. so, with regards to your tanks water surface, make sure that you have an "active" water surface. if you have a skimmer, that should help raise the pH if you have an air tube running out of a window for fresh air to be introduced. also, with that said, open windows to allow fresh air into the room, is helpful as well.
for kh, is it possible that youre salt mix has higher KH in it to start with? and i assume your arent dosing? alk to rise on its own is unheard of, but ive read before from RHF on these boards, that artificial rock that wasnt fully cured might leach it, but then that would depend on how old the tank is. ultimately, if you have a salt mix that has a higher alk content, doing a water change wont actually help, but that again is going to be determined on what salt it is.
of course, a kh, if it keeps rising, the only other thing that i could think of is faulty testing, as kh shouldnt rise on its own.
