What could these scenarios mean:
You turn on your tap, and the water comes out brown; on the side of your house, there are brown streak marks running down the wall; the rebar inside of your cement is expanding and causing it to crack.
These are all indications of a problem caused by oxidation, causing metal to rust.
Wherever there is metal that is exposed to oxygen and moisture there is a risk that rust forms. Once the process starts, the metal turns porous, and worsens the situation.
Depending on where the rust is appearing, it could range from a situation that is unsightly to one that threatens the structural integrity of your home.
Painting over the rust does not solve the problem. It can continue growing under the surface and make the situation a lot worse before it surfaces again.
If there is rust appearing on your electrical panel, you should have it looked at by a certified electrician as soon as possible, because water entering the panel could cause a short or a fire.