I saw this on this site... when I saw the purple stems.....
the 20X3 nutes is just a good all around feed...
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.