Okay, I've read up about voodoo juice a little for you.
And. Its designed to work in coco. So, just use it in the 1st 2 wks of growth and flowering, or you'll just end up wasting a lot of it.
In reality, you'd use it with the likes of tarantula & Piranha, (but that's where soil comes in)
It'll do fine in coco, but, would work best with some soil. But, it states its for coco.
Heres some useful info on coco growing i keep bookmarked.
I'm not big into coco myself.. haven't the time but hopefully this will help.
https://percysgrowroom.com/starting-a-cannabis-grow-in-coco/
Good luck pal
So, just use it as stated.
Your seedling looks fine.
450ppm is a little high. But keep it at that now..and. and sure to give a good flush to rid yourself of salts and so on..