Landlord raised rent $400 with 30 days notice — is this legal?

I've been renting a 1-bedroom in Goleta for 4 years. Last week my landlord posted a notice raising the rent by $400 starting next month. That's a 22% increase. I thought California had a rent cap under AB 1482? When I called the property manager they said the building is exempt. I have no idea if that's true. Can your office help me figure out: 1) Is this rent hike actually legal under state law? 2) Where do I go to file a complaint if it isn't? 3) What protections do tenants in your district actually have right now? I'm trying to stay in my apartment, not move my family across town because someone wants to flip the building.