why the other team's game balls remained properly inflated...given they were undergoing similar circumstances (weather, handling, use, etc).
Properly inflated /= experienced no deflation. The Colt's footballs could have experienced deflation and still met the 12.5 psi limit if they were inflated at the high-end of the range to start. This of course assumes that the leaks regarding the Colts footballs are correct, the initial report of 11/12 Pats game balls being 2 psi under the limit have been contradicted by the repots, including a report this morning that only 1 ball was 2 psi under the lime (the ball handled by the Colts' staff), a few balls were about 1 psi under the limit, and the rest were just a "tic" below 12.5 psi.
They also weren't necessarily undergoing similar circumstances" - the Pats' balls were used more and it could be that the Colts (as a dome team) were more concerned about keeping the balls dry than the Patriots were (homer speculation on my part).