http://www.drugs-forum.com/growfaq/GrowFAQ Basic Topics.htm - some if not most of what i was talking about, youngin. Find this
Nutrient Disorder Problem Solver by Jackerspackle
then read #10.
If you think this is more likely than overwatering you ought to buy a ph test kit from Lowes/HD. The white leaves kind of give it away, i think.
then look for [h=1]
Plant Abuse Chart and Photos by Nietzsche[/h]
and nearly at the bottom, you'll find a more indepth look at FE deficiency
"Caused by factors that interfere with iron absorption of roots: over irrigation, excessive soluble salts, inadequate drainage, pests, high substrate pH, or nematodes. This is easily corrected by adding an iron supplement with the next watering."
Ive never had a ph prob that serious in soil and if youre not overwatering my next guess would be the drainage. Solution? Perlite; of which i dont see any in your mix
Oh and, "I dont think i can grow a plant... smething always happpens", dont be so easily discouraged ;D
good luck