A 28-year-old patient complains of experiencing gum discomfort, gingival hemorrhages and pain, especially during eating, for a week. Objectively: the gums are swollen and markedly hyperemic, especially within the 43, 42, 41, 31, 32, 33 teeth, soft plaque and tartar are present, gingival sulcus is up to 2 mm deep. What is the most likely diagnosis?