Check out this, nitrogen - related def or what? It's kind of greener on the inside with light green outside of each leaf. please help!
First let me admit to not reading the entire thread. Forgive me if I suggest anything you've already posted that you tried. You should test the soil's pH if you haven't already. Test the pH of pure water and water thoroughly. Allow it to sit for at least an hour and the squeeze some water out of the soil. You can press on the surface and collect runoff from the bottom. The runoff that comes out when you water has not had time to take on the soil's pH.