Help Me diagnose a gas leak

I kegged 2 kegs, force carbed and went on a 11 day vacation. I only have one gas in so I kept keg #1 hooked up with 12 psi and left keg #2 with 20 psi pressure in my keezer. When I got home, no gas in keg #2. Tastes kinda flat but can't tell for sure because I have a cold.

I switched hookup to Keg #2 and in 1 day the same thing happened to keg #1. My 5 lb gas is not empty. All 5 gasket/orings are brand new and lubed up. Should I suspect my poppets? I have 2 emty kegs now. Should I start swapping parts?

2nd question: Once you lose pressure in carbed keg does the beer go bad or can you just re-carb it?

The beer probably absorbed the 20lb you originally put in it. I have found that when I charge mine with 20-25 lbs and then come back a day or so it has a little carb. I quickly realized that I need to leave it on the tank for the entire 36-48 hours to get a good carb throughout. At that point you can take it off the tank because the beer has absorbed the right amount of CO2. When you want to serve it just turn the pressure down to 3-5 pounds, depending on your system. You can recarb a beer as well....the gas is just equalizing itself.

I think I understand the carbing methods.

I have a leak because when I test the relief valve there is no pressure release.
My question is where could this leak be?

What relief valve are you talking about?

There are plenty of threads that deal with finding leaks in systems.

Non-scented soap with water in a spray bottle helps as a first step...see bubbles, you got a leak.

Outside of that, I would check all your o-rings/seals on each keg (including the rings on the gas and dispense tubes). Make sure they're in working order, not torn or anything.

And get yourself some keg lube, you won't regret it!

I just sprayed starsan on the poppet valves. Of the 5 kegs I bought 4 out of 10 poppet valve leaked.