yung leaves only curling up

only the yung and new leaves curling up . i tried mg for the past 4 days . any suggestions plant still growing and budding . my lights are 20 inches a way from plants cause i thought thay where to close . thare not fallinf off. thanks

How old are your plants? And what type of lighting are you using? If you are using HID lighting then yeah 20 inches away would be acceptable, but if you are using fluorescent lights then bring them babies closer to the plants, within 2-4 inches. Any pics would be great. And you also might want to make sure that you are not overloading them on magnesium. Yes magnesium is real hard to cause toxicity in plants but they lock out other nutrients. See if your giving it maybe to much potassium or calcium as this can cause magnesium to be bound in the soil.

are they curling up and still green? tips brown?

your light is too close to the plants!