Fatigue during calorie deficit

Hello! I am almost 30, 5’3”, and currently 142lbs. I’ve been in a deficit, with small breaks like a maintenance day or 2, since early January. I’m down 6lbs which is nice. I don’t do anything crazy for exercise, just walking to reach 7,500-10,000 steps a day, and 15-20 minute dumbbell workouts at home 2-3 days a week. For my calories, 1,400 seems very manageable, I’m seeing progress and I’m not terribly hungry. My only complaint is how fatigued I’ve been feeling lately. My vision also blacks out when I stand up. I do have 2 young kids, and it is sick season, so it’s possible I’m fighting something off. I’m just wondering if this is normal and if I should change anything. I’m eating a very balanced diet and eating nutrient dense foods. Also taking Mary Ruth multivitamin.