Minerals in the water . . . acid to get rid of it.how is that acid in the water from overspray?
Oxalic Acid is made from Rhubarb.how is that acid in the water from overspray?
sno-bowl cleaner used to be the go-to.Go to $ general buy toilet bowl cleaner, just like a toilet apply and let soak may take two applications but the stains will be gone.

rhubarb? Cool...Oxalic Acid is made from Rhubarb.
its a naturally occurring acid, just like oranges and tomatoes
Have you tried eating plant food? It might help the bush.My pee is natural but too much kills plants. Ask my outdoor pee bush by my shed and it will agree with me...