Middle managers seem to be the big toxic issue
Communication, Professionality and get a better leadership principles. Push the team in doing better and not creating conflicts like they did in the past.
They need to realise that as a company grows the most inportant part is the people. People management is key. No matter how long you have been in a company you need to evolve with new ideas but also people, building them up and including then in a communal vision.
People managment and leadership and creating good communication of a unified company vision.