Student housing - Roommate problems

[Dean Fiacco]

Hi I have a question. I run a student rental in Florida that's been going rather well up to now. 

There are 3 roommates that are collectively responsible for the total rent (as per our lease). The issue we're having is there is trouble in paradise and two of the roommates have documented the third roommate being in violation of lease (damage from dogs, boyfriend living in home) from multiple angles.

They want us to intercede but not sure what options are without voiding the whole lease for everyone?