Purple Glue in coco

it is not a deficiency.with a plant that big indoors and the light is only from above,lower leaves getting dead as time passes.They can't get enough energy to keep living.Plant looking really healthy,no sign of excess or insufficient nutrients.But,if you decide to flush, keep giving pure water till runoff is more clear colored and has less EC,follow if you have a tds meter.Small,insufficient amount of water will make it use nutrients stored in its leaves.and they will die soon.Yours is not even a big problem,this happens indoors.Nutrient rates are cool,plant can't have a deficiency with these rates I think.and its not looking hungry or overfed.Everything is cool.Keep feeding and if you decide to flush,please flush with adequate amounts of water till runoff gets more clear,then add your regular feeding solution after this.You know its coco,you should be feeding each watering.ph problem would appear on upper parts first.not a ph problem.simply they arent getting light and they are coming close to final.you can remove them leaves and try to keep the other parts green.

Well from the pics I'd say you can start flushing and getting ready for harvest at least. Those pistils will curl in and the calaxes will swell as she finishes up. Leaves still look pretty dark so give her a good flush, and she might lighten or purple up. Then you can totally harvest as she's ready. I bet those lowers just need some light, you got a big plant there with amazing, lightblocking, fan leaves.