Semiconductor lasers' oscillation wavelengths respond to temperature- and magnetic field-fluctuations. As reported in the 1960's, these wavelengths shortened, at lower than 80K, under a magnetic field larger than 4T. This phenomenon attracted our attention, during preliminary experiments, because, when we exposed bulk-type semiconductor lasers oscillating at 780nm to relatively weak magnetic fields (less than 1.4T), at room temperature (300K), we observed that the oscillation wavelength shifted to the longer (lower frequency) side. For this work, we focused on the longer oscillation wavelength shift, the lower power side optical output-power shift, and the higher voltage side terminal voltage shift of a number of multi-quantum-well (MQW) laser diodes oscillating at 780nm, under the same experimental conditions as those used in our previous works. In discussions of these shift mechanisms, we consider how wavelength (frequency), optical output-power, and terminal voltage shifts are correlated. Our expanded knowledge base has forced us to employ mechanisms completely different from those used in studies dating as far back as the 1960's. We are now introducing a mechanism in which temperature rise and the longitudinal magneto-resistance effect cause the shifts observed in our experiments.