There are 4 main culprits. Funny thing is, 2 of them have had good years to date, 1 has been brutal and 1 has been okay.
Wright has allowed 16 (passed balls are probably the main reason), yet the Sox are 12-8 in games he has started (he's personally 12-5)
Porcello has allowed 6; the Sox are 15-6 in his starts (he's 13-2 personally).
Hembree has allowed 6 unearned runs. While he's 4-0, he has either been lights out or bad.
Then there's everyone's favorite whipping boy, Mr. Buchholz, who has also given up 6 unearned runs. No real surprise given his mental fragility and inabaility to handle a little adversity.
The rest of the staff is in the 1s and 2s, so no concern there.