The 6.8 is a lil high, What kind of soil are you using? I would leave the blackstrap alone for a while and just use ph'd water. How often do you water and how much runoff do you allow
6.8 for soil is fine, if the ph meter is accurate. Values over 8.0 and under 5.5 will lock out nitrogen, and other nutrients have different levels. Ideally, soil should be about 6.5, however 6-7 is fine. A soil grower should not sweat 6.8 if it is steady.
Why are you adding molasses at this early stage? Molasses is energy, which the plant can produce on it's own with nitrogen. I assume your soil has nutes, because of the "plus" in it's name. I would put off the molasses until you enter flowering and get your PH checked. The soil should provide nutes needed for vegging.