Flush them out FAST.
Epsom salts are meant to be used ONLY to treat a verified deficiency, which yours DON'T have, and even then, a foliar spray at only a pinch or 2 a quart is more than enough... 1/4 teaspoon per gallon is the soil dose and even that I don't recommend in almost any situation because of the risk of locking out other nutrients, messing with soil pH, or salting up the soil.
If your soil pH is 5, make a solution of tap water at pH 6.8-7 and flush 3 gallons through, then water heavily with a solution of your grow fert at 1/4 strength.