Blue large-amplitude pulsators (BLAPs) are rare, hot, short-period pulsating stars whose rapid oscillations provide a unique probe of stellar interiors and atmospheres. In this paper, we study two short-period BLAPs in the Galactic bulge, Optical Gravitational Lensing Experiment (OGLE)-BLAP-142 (P ≈ 6.6 minutes) and OGLE-BLAP-148 (P ≈ 7.5 minutes), by combining light curves from the OGLE, KMTNet, and DREAMS surveys, spanning 17 yr with cadences ranging from minutes to hours to days. We perform generalized Lomb--Scargle periodogram analyses of their light curves and identify, for each BLAP, three closely spaced pulsation modes separated by ~1%. The dominant mode can switch within timescales of order a year, accompanied by a likely blueward color shift (~0.1--0.2 mag). The yearly period excursions of the resolved mode families imply apparent ∣Ṗ/P∣ values of order 10-6--10-4 yr-1, large enough to mimic or exceed smooth evolutionary period changes. One mode family in OGLE-BLAP-148 shows a coherent decade-long drift at the ~10-5 yr-1 level, but its failure to extrapolate to the earliest and latest epochs suggests a transient mode-family drift rather than secular evolution. Such close-spaced multiple pulsations and mode switching may be common among BLAPs with periods shorter than 10 minutes, and their physical origin remains unclear.