Flush with ph balanced water would be the best course of action. though this plant is not that large so you cant really do that without overwatering her. So its either let her go through a few days until its dry again and then adjust or you can bite the bullet giver her extra water to sort it out but keep in mind this may slow her down. Im not too familiar with growing in coco i know people say its hydroponics but if thats so why are there seperate feeds for hydro and coco I dont know. I know alot about ph though as I am a dwc grower fully hydroponic soil or coco is way too messy and pretty bait if you live in an apartment or somewhere without a garden people see you bringing in soil are going to know instantly what your upto lol If you wanna do Hydro I suggest going the full mile and doing a NFT, DWC, or flood and drain. these systems are what I would call more hydroponic as they dont need a medium :) though I hope this helps and wishing you all the best to sort it. ps stems that discolour or go a bright colour is usually down to light exposure its the plants natural defense against intese light you will notice this when you look in a tent and see its only the stems in the light that turn this colour the others wont :) it could also be genetic though or a mutation of that certain seed or pheno you never know :)