The half-lives of seven nuclei have been determined in the neutron-deficient mass-70 region following their production via fragmentation of a 345 MeV/nucleon Xe124 primary beam on a 740 mg/cm2 Be9 target at the RI Beam Factory, RIKEN. The results include two new (Sr73 and Y76) half-lives and a more precise measurement for the ground-state half-life of Sr74. The new results are discussed with reference to previously published calculations that predict the location of the proton dripline in the light Sr and Y region of the nuclear chart. In addition, differences in the ground-state structure of Rb72 and Y76 are discussed with the aid of density functional theory calculations. These provide a possible explanation for why Rb72 undergoes proton decay while the α-conjugate nucleus Y76 predominantly undergoes β+ decay.