Q.Parrot impatiens
I have an impatiens plants and it was doing really well and all of the sudden the stem feel limp and soft and all the leaves are drooping. I live on the central coast of California. Should I cut it down?

I'm sorry to say but it appears that your plant has died.
It could be root rot from over watering.
Here is a link that will help refresh you on the care requirements if you should try another plant.
https://www.gardeningknowhow.com/ornamental/flowers/impatiens/congo-cockatoo-impatiens.htm