A 52-year-old man with newly diagnosed acute myeloid leukemia (AML) presents to the oncology clinic. He has been started on cytarabine (Ara-C) as part of induction chemotherapy. On day 5 of treatment, he develops severe mucositis, diarrhea, and a white blood cell count of 0.8 × 10⁹/L. He is afebrile with stable vital signs. What is the most appropriate immediate next step in management?