Need more info. What are you growing in? Hydro? Coco? Soil? What nutrients are you using. Are you measuring runoff or slurry ? More info will help get to your answer.
Raising or lowering ph 'quick' isn't a good idea.
5.5-6.0 is a totally acceptable ph range for Coco, but low for other mediums. Like stated above, more info is necessary.
Over feeding with no run off can cause your ph to drop quickly.