it seems like you have pretty low stamina for many players, even considering you have zone defense. I think slow down would be vital in this situation because of that. I see you ran slow down many times recently, but not the most recent game. i would stick with it.
I also noticed your best PG fouling out a few times. I would definitely set his foul settings to least aggressive, hopefully avoiding fouling out.
The same player, Hupp, is also taking a lot of shots. I would consider turning down the distro on him a little bit, lest you risk getting double teamed vs. m2m and zone defense....
otherwise, I think the other comments are right -- your guards aren't that fast and none have that high of defense rating or athleticism. your bigs are very low on athleticism and also very average to bad on defense attribute. that will add up to inconsistent performances.
statistically, you are just barely losing the rebound battles. but with a zone, you really need to win the rebound battle IMO. you aren't designed to win the turnover battle (like a press would be). You need some more firepower on the front line with only 2 bigs that can rebound.... that's a recruiting issue though.