Room-mate Left Because Room Was Uninhabitable, Now We May Have To Pay Her Rent (location: California)

(Location: California) I signed a lease that started September 1. There were five people on the lease and we are all "jointly and severely responsible". We all collectively owe $3500 a month. There is no itemizing the rooms for each tenant. (I'm paying $940 for my room, but others are paying different amounts). There is a room on the second floor that has a balcony that wasn't sloped properly. Instead of the water flowing off of it, it just sits on top. That said, a few days into the lease, the girl who moved into that room said she was staying at a friend's house because staying in that room was triggering her asthma. She hired a testing agency to test for mold inside of the house. Before we got the results back, she said that the landlord said she was able to break her lease. I asked the landlord if we had to pay her rent for October and she said no. About a week later, we got the results back. Among all the molds detected, the most startling were two molds that came back as 10 times higher than outside levels. There have been handy men inside the house repairing the room, replacing carpet, etc (but not really fixing the root issue which would be the balcony not properly sloped). It is ready to be rented again, however we live in a college town and have passed that window of easily finding new tenants. Now we are being told that we may have to cover the rent of the girl who left.

I have been on joint leases before and any changes that were made to the lease had to be agreed upon ALL parties, including the landlord/property manager and ALL tenants. The fact that the room was uninhabitable and the landlord wants the rest of us to cover the rent while she took this girl off the lease without consulting everyone on the lease is not right to me.