What do you do if it is a nitrogen deficency?

[Jenuine]

I've posted before how my plants are doing, which isnt very well.
I think it is a nitrogen deficency. In this case, what can you do for that?
Again, I do not use soil. I'm a hydro girl. I use hydroton as my medium(which is a lava rock).

Can anyone give any advice on how to get them better from the nitrogen deficency? They have grown...but they are yellowish... curled down...(wilty like)...The stems are not wilty. The new growth, isnt opening it's staying closed together.

Right now I'm flushing with regular water. But I need to know how to fix this problem.

 

[Crazy Horse]

What are your nutes like? You might need nutes that have higher N than what you are you using now. Have you had problems like this before with your plants? Have you used these nutes before with no problems?