Or you could increase the top of the water circulation, get more oxygen into the water. Maybe aim your powerheads up a bit more. I;m sure now that they are related as it occurred at the same time pretty much. I try to air out my house one day a week to counter the stale air I have due to my air conditioning.
A neat trick is to take a cup of tank water and aerate it with an airstone in the house for an hour. Check the ph. The do the same thing but have it aerating out side the house. Check the ph. If the ph goes up in the house you need more circulation, if it goes up after being outside for an hour or so with the airstone then it's co2
exchange issues within the house.
LOL I feel like mr wizard. hehe but it did work for me trying to pin down my ph drop.