High pressure gauge drop - concern?

Got a new CO2 tank and once I hooked it up the high pressure gauge went from reading 850 at 4:00 PM and then reading at 760 at 10:00 PM. The low pressure didn't budge and was at 10 PSI all night. Is this normal because of the drop in temperature as we went from afternoon to night time? The tank is not inside the fridge so it will be susceptible to changes in temperature.

After losing a tank due to leaks over the weekend I changed EVERYTHING minus the kegerator itself. New regulator, new lines, new keg coupler, new connects (ditched the quick disconnects, just incase). Did a soap test before leaving the house. I turned the tank off over night after seeing that change in the HP gauge, but not sure if I'm being paranoid or not.