Stems dark maroon, any idea why?

I have 1, 3 week old plant which seems to be dieing for unknown reasons, the lower leaves seem to be turning yellow and brown, the plants only 4 inches tall, and there arent any branches or anything, so it cant be that they arent getting enough light...

But onto the main question, I have 6 others at 5 days old, growing at an astonishing rate, however the stems on all 6 seem to be redish/maroonish, I was wondering why this was...

 

Q1: Put in enough of any type plant and a certain percentage are gonna croak. The objective is to keep the mortality rate acceptable.

The main question: So they're maroon. Some of us have red hair, some blonde, (and some tend to pink.) I've seen lots of healthy mature plants with purple stems; astonishing growth rates, huh. Maybe you're on to something.

 

If your plants are streching overly quick your light might be to far away
this can result in stragely low yield plants.
Are you giving your plants nutrients, if you are they are too young yet
at this stage all they need is water with the correct Ph (6.6-6.9) somwhere
in that region.
Feeding them too early will burn leaves.

 

usually a plant with red or maroon stems is caused by a nute deficiency i believe to be potass..