Possible leak?

Just got into kegging finally. Have a few beers in kegs at the moment while I'm hunting down a chest freezer. I purged the air out of the kegs and put them on 20lbs just to seal the lids.

My question is: I've gone back about a week later and just pulled the relief valves (I'm new to this so I can't keep my hands away). Some of my kegs have pressure, some do not. Is this most likely due to the CO2 going into solution and equalizing or do you think that my posts are leaking? Thanks

Spray with Starsan to check for leaks.

Good call.

Your beer is absorbing most of the CO2 that you used to seal the lid. When you keg: Seal the suckers with 30 psi....purge a couple of times and check for leaks by spraying the lids and poppits with Star-San and then.....LEAVE ALONE. No need to pressure test later on. Unless your naturally carbing, after a couple of days you shouldn't have alot of pressure in the headspace.