I'm running a few of these as well, and unfortunately have had absolutely nothing but headaches. They are the only plants in my garden that have been plagued by problem after problem. They have been slow growing from the start, and just lack any sort of vigor at all when compared to some of the other strains I've grown. However, they do have one thing going for them - consistency. They all look exactly the same, grow the same, and when they show nutrient problems, they all show it.
Once thing I've noticed is that mine had completely purple stems - and I mean completely - from day one. Not a hint of green anywhere.
Recently, I'm getting this problem where all the leaves are turning a rusty brown color around the leaf fringes, then start yellowing, and then some white colored spots around the outside as well. Did you run into anything like this? They are on the exact same nutes as three other strains I'm running, in exact same conditions, and ALL of the PCKs have this problem, and NONE of my other plants do. Obviously something fussy with the plant, and I was hoping maybe you could help me shed some light on what that may be.