its because youre growing in a plastic cup. Right out of the gate i would say its a moisture issue causing some sort of lock up but you say you definitely aren't over watering what does that mean? If its not water then it has to be the soil what is the mix you're using? I flush is a good idea, when the soil drys but I wouldn't amend the soil until you know the cause. If water is the issue more isnt going to help and if ferts are causing lock up more arent going to help.
I have always growing in plastic cups.
I say I am not over watering - it means the soil was dry.
The mixture is nothing special, it is a soil I bought in supermarket, mixed by me with some sand.
The truth is, I usually use perlit, and for those plants I ran out of perlit (I mean, some of those 4 plants getting discolored, plus others looking good).
Edited by rghm1u20, 14 February 2016 - 07:38 AM.