A big part of that is Patrick Corbin has given up more runs than any other pitcher. Gore has given up the 6th most runs. Gore has good stuff though and I have no doubt he'll straighten out and be a better pitcher next year.
Nobody could of anticipated the years Irvin, Parker and Herz have had. They've had some blowup games that have skewed their stats but they've also had a lot of good starts. There should be every expectation with the experience they've gained this year they'll improve even more next season.
They've gone from 6th in the NL in runs against on July 1, to 13th now. Patrick Corbin, while a problem, has almost exactly the same ERA of 5.50 he had then, the decline has nothing to do with him.
-Jake Irvin's ERA has soared, he gave up 16 HR in 62 IP in July and August.
-Mitchell Parker's ERA has gone up by nearly a point
-Average innings pitched per start has dropped under 5.
-Team ERA was 16th of 30 in MLB on July 1, and is now 24th
-Bullpen ERA is 4.16 is near the bottom of the NL, but is still lower than starters ERA
-The defense has fallen to 28th in defensive runs saved. It was 15th of 30 in errors on July 1, it's 29th now.
Irvin, Parker, and Herz might improve, but they've also been scouted much more extensively and the team hasn't responded to that. Moreover, combined they're about 30% of all innings pitched, so bullpen and defensive issues could linger into next year, especially the abysmal defense at catcher.