nutrient deficient?

[indy_chuck]

Here are some images of my young Red Paper Lanterns, what does the darker color within the leaves indicate?
 
Are the plants deficient in a particular nutrient?
 

 
 

 
 

 

[moruga welder]

are all your plants doing this ?

 

[indy_chuck]

Yes, all 6 of them.  4 Red Lanterns and 2 Brazilian Starfish.
 
12 hours of 6000 Kelvin light and at least 2 to 3 hours of sunlight each day.
 
 

 

[DanMcG]

Sunburn maybe?
I had the same thing happen on some reapers early on.
http://thehotpepper.com/topic/71012-discolored-leaves/