New owners of building gave us 3 day pay or quit today [CA]

I went over our problem in a previous post, so I'll make it quick here.

We had bedbugs. We don't the previous owner, he acknowledged the problem, then went MIA for 3 weeks and didn't answer our texts or phone calls at all. We were forced to treat the bedbug problem ourselves for $600.

The previous owner reappeared a couple days after treatment and agreed to split the costs 50/50 with us, saying to take $300 off our next months rent. Then the next day we find out he sold the building to a cooperation.

The new corporation is now telling us this "isn't their problem." We paid rent today, minus the $300, and we received a 3 day pay or quit notice a few hours later. Meaning of we don't pay the $300 in 3 days we will be evicted.

Is there anything at all we can do?? How are they claiming this is not their problem?? If someone had a broken AC before they bought the building is it now not their responsibility to fix?? I'm very frustrated and annoyed, and I'm contemplating going down to their office tomorrow to fight it.

Any recommendations on how to handle this? We obviously do not want to be evicted, but also don't want to eat the entire $600