Backyard Aquaponics
A place to discuss aquaponics

My setup has been going for about 8-10 months and has a 150 gallon swimming pool for 20 +/- tilapia that are about 5 inches.
There are two grow beds both about 35 gallons one containing some tomatoes and the other containing some beans and a baby banana tree (like 8inches tall).
The tomatoes have been slowly dying for the past month and I have no idea why, they're basically dead at this point! There's no saving them, but before I replace them I need to know what went wrong. I even tried buying some hydro additives to add to the water and a ppm meter to double check, but the levels are fine. pH is neutral; fishy are super healthy and happy. The beans started out strong and are now a little wilty. The banana plant is healthy and growing...
What's going on?

There is probably a nutrient deficiency either potassium or iron but in order to get an idea of what is happening pictures would help. Usually with iron the newer leaves will turn yellow compared with the older leaves. With potassium the older leaves will turn yellow and/or die along the edges. Other things could be going on so it's best if you can post up the pics

Pictures would help us help you. Some further details would help as well?

Feed amount
Growbed square footage (or a picture)
constant flow? timer? ebb and flow?
Are fish happy? Eating?

Welcome to the forum!

Bananas love potassium, that could be your culprit, it's stealing from the other plants.

try adding direct to grow bed and/or foliar spraying for nutrients.
also try some blood & bone direct on the grow bed for tomatoes along with potash.

also what are your daytime temperatures ? Tomatoes can die off in full sun and high heat.
(but you are quite a way north so probably not the issue)