Yes, I routinely use a dilute solution of epsom salts to feed my plants, the added trace of magnesium and sulfur is very important for plants -- many commercial fertilizers lack those nutrients.
On the other hand, I'm trying to help dissolve stumps with a slurry of potassium nitrate. Now that added nitrate aids fungal attack, and should also be boosting plant growth, but as a slurry, it burned the grass.
You haven't created a herbicide if you make a strong ionic strength solution. You haven't created a herbicide if you use a high powered hose of water to flush plants out of sidewalk cracks.