Earlier managers had 5-7 subordinates, however, now they will have 30-50. Therefore, they will be expected to be assisted by Asst Manager or Sr Executive. This means hereafter there could be one more layer of hierarchy between a Manager and the lowest rung of the staff.
In view of the additional layer, Managers need to know how to keep an ear to the ground. They just cannot believe what their immediate subordinates say. Therefore, managers need to be taught the importance of upward communication.
While managing 30-50 people one more challenge is conflict within the team members. Human nature is different. Therefore, their personality and way of thinking could be different. Against this backdrop, there could be face-offs or run-ins within themselves. Therefore, Managers need to be taught Conflict Handling Skills.
Going further, managers hitherto handled a team of 5-7 persons. Their team will be enlarged to 30-50. This demands a higher level of team building skills. Are they capable of handling the team of that size?
These are some of the things that I have written based on my common sense. The exact solution cannot be given as we do not know the nature of your industry, the systems and processes, education level of the employees and so on.