Tata Motors — Bubbles on body at various places

I bought TATA ZEST in June 2016. By the end of 2019, bubbles appeared at various places on body. I contacted dealer for reapair in January 2020. They said its not a manufacturing defect but the water we use to clean the vehicle. We have 400+ vehicles in our gated community and all the cars are cleaned by water from a same tank and none of the cars have this issue except one more Tata Zest. In my view its a paint defect .