I think it may be, in part, that you had some guys - particularly pitchers - who overperformed last season and come back to earth (or have slightly worse than expected) years this season.
For example,
Ajax Patel - he gave you 124 IP at a 3.04 ERA last year. That's significantly better than I would expect for someone with his ratings, esp. in Texas. He's struggled this year, with a 6.50 ERA.
A new callup who isn't helping matters is
Beinto Uribe - he was in AAA season, which may (frankly) be where he belongs. Instead, he's been holding a spot in your rotation, with 14 starts, 56 IP, and a 6.27 ERA (1.88 WHIP). Pitchers with a control as low as his (45) generally have to be exceptional in some other facet of pitching, and he doesn't have that to compensate. I'm not surprised at his struggles.
Overall though, I do think some of it is just a product of statistical variation. While your overall team numbers aren't as good as last year, your expected win % is still significantly higher than your actual win % at this point (.493 to .378). It's largely due to you struggles in 1-run games, but that again is something that you probably did better than you *should* have last season (29-14) and worse than you *should* be doing this season (8-25).
Make the changes that make sense (for ex., maybe shore up the pen to bring that 1-run record back up next season), but there are times when you just chalk it up as a lost season (esp. if a similar management/ownership style has a proven track record of success).