With and alk of 9.2 your PH shouldnt be that low. Of course you know that. My first thought would be oxygen levels in the house since your in Ak. Im sure you've had it seal up tight for quite a while. Do you run a skimmer. Do you get any surface agitation from your pumps to help O2 exchange? Is your house new or old? How airtight is it? You'd be suprised what an airtight house can do to regarding O2 depletion. It isnt noticable to us but your tank may show it. The easiest way to test it is to take a cup of tank water outside and run an air stone in it for an hour and then test for PH. If its higher, then figure out a way to get more air to your skimmer without freezing the house. Sometimes even an airline outside of the stand helps.
You from the southeast, or anchorage area?