Best of luck fella, you will be fine but let us know ok. lots of diffrent views for you, but only you will know what you have been doing etc.
Really simple. Why do people over-complicate shit?
It's one of these two things...
A nutrient defeciency OR
Nutrient Burn
Right? So we are all at least agreed that you don't have the right levels of nutrients. You came back and said you didn't clean the hydroton before you started. Basically admitting that there's no way to know how much of what is in your water at this point.
So what's the simple answer? I would clean the hydroton thoroughly...just run it through with clean ph 5.5 water and clean all those rocks.
Then, empty the resevoir, clean it thorougly and refill with fresh ph 5.5 water @ 100ppm. Raise the ppm by 50 each day and you will see the plants turn around.
Whenever I'm in doubt as to WHAT is going on, just start it over and make sure to get things back on track. Don't overdo anything, don't set your ppm @ 200ppm in one day (if it was deficiency and you had no nutes they will likely burn).
Just start them off easy and you'll be just fine. Just get your house back in order.