I am new to the growing world. My plants were doing great then suddenly the bottom leaves started turning yellow. It starting at the tips and edges and progressed up the plant. It is also wilting and some leaves are curling. I have two plants and only one is doing this. Through research I figured it was a deficiency and added T-Rex Grow(nitrogen, phosphorus, potassium, boro, magnesium) five days ago. There hasn't been any change, except my other plant which was strong is now starting to wilt and the tips have turned brown. I water them every 4 to 5 days(a couple ounces at PH 5/6ish) each time. They are in a room with sufficient airflow and are on a 400 mercury light(18:6) schedule. Attached are some photos. Any feedback or suggestions would be greatly appreciated. 
