Near instant inhibitor respawn

I just had a glitch lose a hard fought (win) for my team, after a series of dis-coordination and such. We aced the enemy team as they attacked our nexus, rushed to theirs and destroyed two inhibs. We immediately pushed our full team to the nexus and were attacking it. We got it to about 400hp before we died, and immediately, one minute later their inhibs respawned, costing us the game shortly after. Why exactly this happened we don't know, but, even in the replay, we only took about a minute to attack the nexus and die, and one more to respawn before both their inhibs respawned. Two minutes is the new inhibitor respawn or something?