@Chow The sweet spot for soil is pH 6.5… However, at 6.8, you’re fine, just water at a pH of 6.5… And by the way, the range of acceptable pH in soil is between 6.3 and 6.8
By watering at pH 5.8 you’ll risk deficiency (P, Cal,Mg and possibly N and K) by too low pH (sorry @Myfriendis410)
~Al 
