Turn up the thermostat and check again tomorrow.
What frequency changed? If all modes moved the same, it suggests the oscillator that is drifting is common to all modes. Being you have already done an alignment, I assume you can figure out which oscillator is the culprit.
Random thoughts follow...
Do new electrolytic capacitors need time to reform? If they sat for a few years at the factory, their characteristics may have changed in the first week of use. If a cap is used to stabilize a tuning voltage, maybe that slight change in leakage resistance cause it to shift.
Maybe there is a bad trim cap or pot that changed value from being slightly jarred around. Had that happen in my washington. Alignment went great, radio worked fine, a few days later, I was 400Hz off. Moving the radio on the desk was enough to make it abruptly change frequency. Lightly tapping on the trim cap sent my frequency all over the place, problem found! A wore spot in the clarifier pot can do this too.
What about wax? Every radio I ever had with wax around the oscillators was rock solid. Maybe that is enough?
I can't remember where I heard this, but I remember something about physical shocks causing the drift characteristics in a crystal to "reset". I wish I had dug further into that when I came across it because I know nothing more about the subject. I have no first hand observations of this happening, but if it is true, perhaps giving the crystals a little tap before alignment might reduce the odds of it being off frequency later down the road if the radio does get bumped. I'm not advocating hitting your radio with a hammer, just set it down hard a couple times before alignment. It's going to happen eventually.
