Dish Drainboard

I have hard water stains and the rack. The board is a brown drops of water on the dishes on it. How do I get rid of spots?

Is this wood? Then use a spray bleach. Although its use of wood, not far from the lime or lemon juice and borax paste.

Sos pad and Scrubb gently in a circular motion.

Bleach still works better. Dilute in water. Approximately half / and half in a spray bottle. Add a few drops of essential oil of lemon if you can not tolerate the smell.
If that's bad, buy a new one. They are cheap in a second-hand shop.