petioles turn purple due to p-def, but the apical meristem turns purple due to S deficiency.
however, if your concentrations, pH and ratios of what you feed are not proper, that can cause any and all symtpoms you see.
So, do a little research and calculate what you feed in ppms (i have a spreadhseet linked in profile comments for this). This will help you deduce if there's something missing or adding too much. Make sure to water with 20% runoff every single time. this will avoid buildup and maintain consitency for the plant. let in coco, you don't let 1" dry, but try to do the wet/dry cycle with a little less dry in coco than soil.. it should never dry out like soil an entire 1" deep.
going from coco to supersoil, may cause a little tranistion for plant. It could also be related to what you see, if it preceded the symptoms of course.
I see conflicting symptoms. My money is that somethign is out of balance and fixing that will likley fix your problem.