Bay Area houses silver coating

Bought a home recently in the east bay. A week living in the home, started to hear a drip when using upstairs bathroom. Called in a plumber to get it inspected and he said the seller contractors covered up a lot of shit and there’s a lot of water damage and the dry wall started to bubble up.

I’m furious how the inspection report had no mention of this and sellers conveniently covered it up. Is there anything i can do now to go back to be sellers and dispute?

Also how serious are the water leaks for a two story home. Should i get it fixed ASAP or can i wait for a while to see how the situation develops.

First time home buyer here, so this is causing a lot of anxiety and frustration.