1st grow. Help with my plants! cant figure out what the problem is

I have reduced the light from 600 to 450 watt mh. Watering with botanicare pure grow every other watering, in between with cal-mag mixed in distilled. Using mg organic choice potting mix. I know but it's all I can get around where I live. Watering every two to three days. Plants in three Gallon pots. Looks like heat stress but my light has always been about two feet away. Can someone help me out. These plants are seventeen days old from the day they popped above soil.
 
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