Ph in all the water I mix is low all the time once I add it to the tank the air gas exchange levels it out , I run a steady 8.4 adding 10% of new water brings it down just a tad to around 8.3 letting it run in the tank 24 hrs you will see your ph rise back to it's normal levels , no reason to stress out over a discrepancy in ph levels , If I stressed out over every little thing in my tank I would have made it crash by now , as long as you have good air gas exchange on the surface you are set ,
if you ever read back on a lot of the older threads you will see how many have started dosing all types of additives than wondered why there was so many issues ,
the ocean isn't dosed why should your tank that's how I look at it ,
we all see changes in ph levels at water change 10% isn't going to change things much
running in the tank will help it level out it just takes time
you don't want to add fuel to a fire so why add fuel to your tank