High school teacher needs help

[WAbedroomponics]

Hi guys,

Went back to my Bio/Chem class that I had last year (which got me hooked on aquaponics) and my teacher asked me to look at a system and figure out what is wrong. I thought I would probably figure it out or at least have an idea of what is wrong but I have no idea.
Here is a list of info about the system:
1. All other systems in the green house are doing a lot better than this one.
2. The fish seem perfectly healthy and happy.
3. Water test came back pretty good nothing out of the ordinary.
4. When the plants started looking bad they added 2 grow lights but saw little to no improvement in plant health.
5. The teacher also started adding a nutrient supplement when the plants started looking bad (she got the supplement at a garden store and doses according to the directions)

I will add the photos I took of the plant. One of the main reasons she wants to know is because the supplement was really expensive and she doesn't want to waste it all on one system unless it will help.


Thank you for any and all help she will greatly appreciate it.