Help, please. Some kind of deficiency on my AC plant.

My Acapulco Gold clone is showing spots on the upper leaves.  Pretty much just the topmost leaves.  I'm still in Vegetative state.  
 
I made a rookie mistake and am using MiracleGro Organic.  I've been warned NOW that it is probably a deficiency of some sort.  
 
I'd appreciate some help identifying it.  
 
 

 
and my current setup:
 

 
The AC clone is on the right from this perspective. 
 
Thanks in advance for any help. 
 
Pat 

 

Thanks very much.  Definitely looks like a calcium deficiency.

 

Thanks, Mayor... in fact, thanks to both of you.