Why does pressure go up after a few days?and problems carbin

I have 3 kegs tapped right now. why when I set the pressure to 12PSI and then check it a few days later find it higher like 16-18?

I lowered it back to 12psi and purged the kegs just once quickly but now my beer after 2 weeks is not carbonated enough or no head retention. Should I be raising it higher to around 14? i am using 10ft of dispensing line to the perlick tap.

Any tips?

Any temperature fluctuations on the gas cylinder?

I have seen this on a kegerator I have in an not consistently heated room of my garage.

???

Good Luck

Are you setting your regulator to the psi you want before you open it to your kegs? That always fixed my problems. However, I never had it shoot up over where I had set the psi; only below.

Jacob