Having a refugium on a reverse photo period will help keep ph stable. It will need to be at least half the size of your display to have any effect though.
Drip Kalk. Kalk has a ph around 12. Make sure your tank is getting enough oxygen by breaking surface tension. Plus oxygen levels will be lower in your house during winter months since all your doors and windows are closed. I run a 1/2 inch line directly outside that supplys my skimmer with fresh oxygen rich air.
I have gas heat, and in December my Ph was 7.5-7.8. I opened the windows to the room where the tank is and got it up to 7.8-8.1. Now that I'm dripping kalk my Ph is about 8.0-8.3