Aquaponics Help

Hi Peeps. Taking over for a friend.
Clone and Veg Room
The room has (3) growing tables, (1) 75-100gal reservoir and (1) 55 gal fishtank. The (3) tables are fed by the reservoir and they flow back to it as well. Seemed interesting but now the plants are starting to have problems. Ive personally always used a soil medium and have been able to make nutrient changes to bring the plants back to optimum growth. Not even sure what to do here... The way I understand it is that the fish are responsible for the pH and nutrients. It all seems and sounds great that its self sustaining but what is one to do when theres a problem? Blame the fish? LOL.

I either need to gain some understanding of this aquaponics or convert the room to hydro... Which im not exactly sure how im gonna do either......
HELP!
B

there's very few aquaponics threads on this forum so not sure how much help you will get here.
I have no idea but out of curiosity, why is the fish tank separate from the rez? How does the fish goo get to the plants? I thought the point was the fish water gets pumped to the plants to fertilize them. Sounds like you have hydro with a fish tank in the room. lol.