I have multiple. I tend to grow peppers and tomatoes separately, although I currently have cherry tomatoes in the pepper system since I ran out of room in my tomato setup. We'll see how they do on the lower EC with a different formula. When you drop your nitrogen for the pepper fruiting stage, you don't really want to do that for the tomatoes.

I do grow some cucumber with the peppers and eggplant with the tomatoes. Some eggplant and tomato varieties are fast and massive growers that eat like a teenage boy.

I have my tomatoes seperate as they are heavy feeders and very thirsty, I grow all my cucurbits together along with a passionfruit vine, my winter veges cabbages, peas, chard also all go in the same system, another one from my rhubarb and cauliflower, alltogether I have 7.

It is a job but this year I have added a cheap float values to each container so don't have to keep topping up each resorvoir with water.

I keep them separate, but usually only grow peppers and tomatoes. I did stick a couple of eggplants in with the peppers a few years ago and they did fine.