Beer went flat, no leaks....WTF?

[Kealia]

This one has my a bit perplexed. Both of the kegs currently in my kegerator are now flat.
Both were set at 12psi for weeks and were decently carbed a few weeks ago, but now are not. Over the last few weeks they've gradually gone down in carb level and I've tried to adjust by raising the psi on my regulator to compensate to no avail.

I've checked again for leaks - nothing. I still have plenty of gas in my tank so I'm a bit confused as to what's going on here. I've checked my temps, too (managed by a JC).

Since it's both kegs, i'm thinking it's not the kegs at this point. I'm wondering if it's either my CO2 tank itself or the regulator. To check, last night I switched out both (because it was quick and easy). I bled the kegs down to nothing, attached my secondary tank and regulator and set it back to 12 psi. I'll check this weekend to see how they are doing. If carbed, I can say it's narrowed down to one or the other (tank or regulator) but if there's no change I'm not sure what I'll check next.

If anybody has any thoughts, I'm certainly open to hearing them.

[Beer-lord]

My first thought would be the regulator too but even if I take the CO2 off the keg for a number of days, my carbed kegs are still decently carbed so I wonder if it could be the fittings and not the ball locks. But if that were the case, you should see a tank getting near empty. It is baffling.

[Kealia]

Yep, everything is sealed tight so I'm really thinking it's the regulator or some issue with the tank dispensing. This is the tank I get filled rather than swap out because it's pretty and shiny aluminum instead of steel. If it turns out that the secondary set up works I'll swap my primary tank out keeping the regulator that's on it to narrow down the issue.

Keep yer fingers crossed for a carbed test pour on Friday. I have at least 1G if not more of my Nelson Sauvin and IPL in those kegs. The good news is that since the kegs are sealed I'm not really worried about them getting oxidized - just losing some hop presence due to timing now.