It won't hurt the plants because they won't take in anymore than they need, not if you're foliar feeding. The only thing you have to worry about, is underestimating it's effectiveness, then giving it too much fert in the soil, causing fert burn. Foliar feeding is claimed to be 8-10x more efficient than root uptake, of nutrients, which would make it pretty easy to sustain a vegging plant, on foliar alone.
I'd like to do an experiment someday, and try feeding a plant with nothing but foliar feed. It'd be cool to see what kind of results you would get, discovering if you could sustain them til harvest(and healthy). Hmmm.....