Diagnosis
This is hard water scale. The internal water softener system in this model is either depleted or malfunctioning. The dishwasher uses a resin tank and recharge salt.
How to Fix It
Manually initiate a recharge cycle. Press Heated Dry, Sanitize, and Start buttons simultaneously for 3 seconds. The display will show 'rch' and the cycle will run for about 90 minutes. Add dishwasher-specific salt to the reservoir in the bottom tub if low.
If That Didn't Work
The softener solenoid valve (part WR49X10051) may be clogged or failed. Check for voltage at the valve during a recharge cycle. No voltage points to the main control board.
Heads Up
Only use regenerant salt made for dishwashers. Table salt or water softener salt will damage the system. Recharge cycles use extra water and heat.