I haven't had this issue myself (i just set and forget for a week or so), but here is what i would try:
I would start by taking it completely off the gas and purging the head pressure.
Then i would warm it 5 to 10 degrees force more CO2 out of solution.
Over next 24 - 48 hours i would periodically pull a sample to see if it is right yet.
If not, purge pressure and let sit for a 4-6 hours and test again.
Once you get to where you like it, put it back on gas and chill.
Assuming your serving pressure lines up with your carb level @ serving temp it will further balance out over additional time.
DISCLAIMER:I have not done this personally, but it is what i would do if I needed to. Your results may vary, or I might be smarter than i thought.
Cheers and good luck
