Are the gauges holding steady at 12psi? +1 to nebben, after closing up the kegs, hit them with CO2 and release a few times to purge oxygen and then hit it with about 20-30psi to seal the lid good, release again and then set to your carbing pressure. You can spray some starsan around the lid and posts and look for foaming to check for leaks.
Draft 3: Belgian Dubbel
Primary 1: German Hefe