I thought that I replied to this but i guess not... The biggest problem with baking soda is the soda or sodium(Na). This will cause a lot of problems including but not limited to; Very high salinity aka toxic salt build up, haywire PH and TDS readings, and the worst nutrient lock out because of menerials perciprating out of the solution.
Trust me, I would rather leave my ph too low, then add baking soda. Even flushing with tap water would be alright as tap water is usually around 7 on the ph scale.