I found this and i'm new so , why not spread the word. This thread pretty much brakes it all down for you in every way possible for a sick plant. Enjoy.... http://www.icmag.com/ic/showthread.php?t=11688
This is a fantastic thread. I've been using it to help understand the conditions of my plants. So far I've only identified some nitrogen deficiency and overwatering but I couldn't have done it without this thread. It really helps to have pics and not have to post pics to get an answer because sometimes I'm not in range of internet access.