I know exactly what is causing that and the good news is it is fixable!
Its called efflorescence. Its essentially the salt seeping through the bricks. What has happened is that when the bricks were being laid, it rained and water got into the cavity. As the bricks dry out the high salt content in the clay is being drawn out with the water.
The solution is to not panic and wait for them to dry out, which could take 3-6 months depending on the whether. Once they have dried out they can be pressure washed clean.
There are various chemicals that you can use but i dont think they work as well as just waiting for the bricks to dry out.
I had this on approx 30-40 homes and it all resolved itself despite some very worried clients
good luck