We use potassium chloride in our water softener system because we were told that salt will harm our plants. The runoff from the system is buried about 2 feet in the ground below one of our plant beds. The evergreen plant closest to the pipe is beginning to show some sort of distress (needles are turning brown and falling off and shrub is turning yellow). Could it be getting too much potassium? The rest of the plants in the bed are OK.
Yes, it could be the results of salts building up in the soil.
A soil test is the best way to determine if this is happening.