Blanks's two-run homer, his only hit, came during a six-run second.
David Eckstein had three hits and two RBI.
Chase Headley had three hits and one RBI for the Padres, who have won three of four.
The winner was starter Kevin Correia (9-10).
Florida's Wes Helms had two hits and two RBI.
Chris Coghlan had three hits and one RBI.
Cody Ross had two hits and one RBI.
John Baker drove in a run, and Hanley Ramirez had two hits for the Marlins, who have lost seven of 11.
The losing pitcher was starter Kevin Correia (9-10).