Investors, customers, competitors and suppliers come under which forces of business environment?

Specific

Business environment includes both specific and general forces.

Specific forces (such as investors, customers, competitors and suppliers) affect individual enterprises directly and immediately in their day-to-day working.
General forces (such as social, political, legal and technological conditions) have impact on all business enterprises and thus may affect an individual firm only indirectly.

Thus, Investors, customers, competitors and suppliers come under specific forces of business environment.