My experience with planting vegetables in container was a great learning opportunity, I've learned that small containers are not suitable for fast growing vegetables, I had to transplant all of my garden cress into the garden soil, not only my hanging garden, even my bigger containers encountered the same problem of running out of nutritions.
As you can see those are pretty big chunks of soil but the roots just reached the bottom of the container and the leafs started to go yellow.
The garden cress grows extremely fast but they need a very rich soil and they are extremely delicate, just watering them can bend them down and damage them.