Yes most likely due to rotted roots from sitting a bit damp early on.
It's the same thing I saw when I tried fine pith coco years ago. Very temperamental in the beginning until you get a good root base in to it then it's still just okay in my experience. It was always a struggle using an automated system with timed feedings until the plants got 12" to 16".
I still think you should use it as an experiment aka lesson and see if you can bring it back to health. If it dies it dies.
Nothing ventured, nothing gained.