I have 4 plants growing now for 2 and a half weeks. They were from seed - Top 44 - which I bought because it's supposed to be good for first timers. The area is 1 meter square with white walls and a 400w grolux hps light set about 18" away. I used miracle gro soil. All seemed to be fine until about 2 days ago when I noticed that one is turning yellow around the edges of the leaves and all 4 are curling. Help!!!!!!!!!!!!!!!!