They get plenty of water. I notice another plant I have on the lanai does the same thing but not to the same extent. Giving them six hours of sun doesn't seem to make any difference.
It sounds like too much water has caused an infection. If the soil doesn't have some time to dry out between watering, then plants can contract infections. Usually, if the new growth is coming out already infected, it is too late to save the plant. Sometimes, you can, but most often it will result in the death of the plant.
Now you will have to treat the area and plants with fungicides. This will help kill off whatever is lurking in your soil. You may want to plant new plants that are completely unrelated to avoid spreading the disease to other plants. This article will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
I want to get a white birds of paradise for my room, but my room barely gets any light. I was wondering if no - little light would keep the white birds of paradise small, or would it just kill it? I want it smallish and no flowers, but I don’t want to kill it
Looks like the low light will do the trick. Add to that low water and frequent repotting. Just do the opposite of what is described in this article:
The plant is about 3 feet tall and otherwise healthy.
You can trim out the damaged stem. Here is more:
Not sure what’s wrong!! To much light to much water or not enough water!! It sits next to a window!
I do see signs of bacterial infection. I would use a fungicide of your choice, and keep a careful eye on watering.
If your container has a saucer that allows you to remove all extra water, then do so after watering. Water once the top 1/3 of the container soil is completely dry.
If your container does NOT have a removable saucer, then you will wait until it is dry down to about halfway, completely, before watering again. This will prevent infection.