I'd say the realistically fixable thing is pre-snap penalties. Fix those and you sustain more drive. Bills score more points. Teams start to change the way they defend the Bills and longer passes open up more.
The second thing is to keep Allen focusing on not making mistakes. Defenses are ok with him beating them on shorter routes because they assume he'll make a mistake eventually. When they have the penalties come down and Allen doesn't make mistakes, they have to start stopping the shorter game and that opens up the longer game.
They also need to figure out the run game. They've been able to move the ball, but the run game is either in-frequent, ineffective or both. The last drive Tenn knew the Bills were going to run and couldn't stop it. Where was that earlier in the game?