3 lanes of super creeps loses to no minion wave push

So i just finished a game that went 65 minutes. In which my team just got all 3 inhibs, then 2 of us died, then the enemy team pushes mid WITHOUT a creep wave, but manages to out dmg 3 lanes of superminions that beat the team to the nexus turrets and nexus, there were at least 12 waves of creeps with at least 10 siege minions, but the enemy team with no creep wave, NOTHING can push into the base and take down turrets faster. isnt there supposed to be a dmg debuff against turrets if you have no minion wave with you?