Purple stem and leaves on marijuana seedlings

Also the growth has been stunted.

Water them slowly and allow the water to absorb from the top of the pot down.
Water them when the top inch is dry.
Keep the nutrient water PH between 6 and 6.5.
It loves light, but be sure the light heat is not too hot on the top of the plant.
No need for any plant support at this time.
Circulation should just barely wiggle the plant. That will make the stronger naturally.
Temps are good. Night/Day.

The purple strain is crossed with many other strains to make some delicious tasting and smelling stuff. Some times variations happens from plant to plant. I have blue dream in each of my seasons. In cooler seasons the leaves turn purple for sure. If I see it early on, I don't worry about it.

Photos?