The patient who was taking an oral corticosteroid for the past month to treat a breathing problem has been tapered down and off the drug. One week later, she has all of the following changes. Which one do you report to the prescriber immediately?
A. A 1-pound weight gain
B. Serum potassium level of $6.2 \mathrm{mEq} / \mathrm{L}$
C. Continuing scalp hair loss
D. Thick white coating on the tongue