slight to moderate ph inbalance hense nutrient lockout by the looks of that fanleaf you got one hell of a phosphorus defeciency the give away is that purple stem uneven watering also seeing as how one part of the leaf is affected an the other isnt heres a nice quote an link:
Phosphorous

Phosphorous is used for plant energy by being assimilated into molecules called Adenosine-tri-phosphate, or ATP. This molecule is necessary for any plant activity that requires energy such as root growth, flowering, respiration, and vegetative growth.










Phosphorous deficiencies are distinct. Purple stems, leaf stems, leaf veins and stunted growth are a sure sign of a Phosphorous deficiency. Leaves will also tend to be smaller and dark green, and may or may not include necrotic patches. Bud size will be smaller and underdeveloped, as will the root mass.

A good all-around fertilizer like Peter's 20-20-20 will clear this up.
http://www.overgrow.com/growfaq/1382