Certified GKH Gardening Expert
That particular patterning is an infection from overwatering. Those spots will not go away, but you can stop the spread.
Mix peroxide with water at 1/4 peroxide to 3/4 water and water this in once per week for 3 weeks, or 3 times over 3 waterings, if it doesn't dry within a week. This will help to kill of the infection.
Make sure that you have a way to pour out any extra standing water that will accumulate in the very bottom of the container. If it does not have a way to drain it out, then you will have to be extra careful when watering and make sure that it get dry almost all of the way down the container.
If it does have a way to drain, then just make sure to water when the soil dries down to 2 inches or so, completely.