Q.killing moss
I have an Aubretia bed growing on top of a stone wall about 30 ft. long. It has recently been invaded by moss. The bed drains well and the Aubretia plants appear healthy. Is it possible to apply something that will kill the moss but not harm the Aubretia!!
You could start with a soil test, it can help you determine if a low ph may be a cause of the Moss growing in your garden bed.
If you do use a Moss killer application, you will need to check the label to determine if it is safe to use with your plants.
This link has more information.
https://www.gardeningknowhow.com/ornamental/foliage/moss/killing-moss.htm