Q.Why Are My Lemongrass And Citronella Dying?
I planted citronella, lemongrass, marigolds and rosemary in this pot and they grew really big. Just up until last week they looked beautiful and now they are all turning brown. What did I do wrong?

Certified GKH Gardening Expert
It could be likely that they're too crowded, together. This, or possibly that the soil is lacking in nutrients.
You can test for that, though. These articles will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
You may, also, want to keep an eye on soil moisture. This article will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm