I've just gotten a hand me down CO2 tank and regulator. I also just kegged my first batch so my experience is very limited. I got the tank filled, hooked up the regulator and started force carbing my keg @ 40 degrees. I noticed that according to the regulator gauge the pressure in the tank has gone down noticeably. I checked my connections with a soapy water spray and found no leaks. Is this due to the CO2 shrinking because it's being chilled?