Reporting An Illegal Bedroom In Los Angeles?

I'm at the end of my rope with the situation I'm in. I live in a one bedroom duplex in Los Angeles with my wife and for the past three years I've had a single person on the other side of the duplex which is also a one bedroom. Unfortunately, she moved out in September and the landlord decided to rent the unit to a family friend of hers. The problem is that they're a family of five people; three adults and two children under five. The noise has been nonstop since they moved in, the plumbing has clogged five times, they smoke weed constantly and it's honestly been a nightmare. The most recent wrinkle is that I found out that they converted the storage shed the unit has outside into a bedroom for one of the toddlers to live in. I'm not well versed in Los Angeles tenancy laws, but I have a few questions. For one thing, is their use of the shed as a bedroom illegal? Could the landlord get in trouble for it? Could they be evicted? Secondly, with the unit only being one bedroom, are they over the limit with five people? I'm honestly just looking for anything I can use to root them out and claw back some sanity. Thanks in advance for any and all help.