Do you mean drift as in the ph in the run off in a week?5.8 for hydro, 6.2 for soil. I'd go a bit lower depending on if you have drift for hydro. For instance, if in a week your PH is 6.2 from 5.8, I would lower my PH to 5.4 to let it drift up to 5.8.
Different PH's result in different nutrients being introduced to the roots. What nutrients are you using? To beef up that stem I suggest Protekt from Dyna-Gro.