Blake cracked a three-run home run and Ethier had a solo shot, both in the first inning. Ethier and Matt Kemp each had two RBI for Los Angeles, which trails the first-place Diamondbacks by 2 1/2 games in the National League West.
Lowe (11-11) worked six scoreless innings, yielding four hits.
Relievers Scott Elbert, Cory Wade and Jonathan Broxton tossed an inning apiece.
Mark Reynolds hit his 26th homer of the year for the Diamondbacks, who have lost six of their last seven contests.
Loser Brandon Webb (19-6) failed in his second straight start to become the National League's first 20-game winner this year. Webb was rocked for eight runs and eight hits in 3 1/3 innings.