Why does our Offense suck so much in the second half?

Here's a stat for everyone: We rank 4th in first half Points per game (14.7), but we rank 26th in the second half (9.1). We rank 1st in Time of Posession % in the first half (56.73%), but drop to 16th in the second half (50.39%). How is it that we seem like a somewhat competent offense in the first half, but are below average in the second half? Does Slowik tell the guys at Halftime to not play hard in the second half? Is there a stamina issue? Are we running out of gas? I'm not particularly happy with the overall offense, including the first half, but they're not as bad. I just don't get why we can't play 2 complete halves of football.