Tap water is mad to have a higher Ph to eat away the calcium deposits in the pipes.. When you run the Tap thru an RO
unit it will lower the pH.. I would try and Open a window close by and see if that helps.. Also make sure there is alot of surface movement to inhibit Co2
exchange.. Increasing the surface flow.. Removing the hood if its a glass hood... Opening a window should all help with bringing your pH up.. BTW
test towards the time the lights go Out.. your pH will always be lower in the early am.. Mine usually stays between 7.9? and 8.1 since my calcium reactor and before it was 8.0- 8.2 But if I closed a window I could watch the number drop at least .1 depending on how many people were in my house at that Time..