I have never had severe hemoptysis but the times I have had blood tinged/streaked mucus or even a little bright red blood, It was either a direct result of an infection/inflammation that I either have (MAC) or am fighting or I've gotten too aggressive with airway clearance coughing after doing 7% hypertonic saline. The pulmonologist typically advises stopping airway clearance for 24-48h until it clears up.

Recently, It was bitterly cold and I went for a walk on the beach and the extreme cold and wind caused bright red blood to come up as soon as I got back to the car and I read that cold narrows the airways and the cold, dry wind irritates already irritated airways so I learned my lesson with that. I drank warm tea and gave airway clearance a break and it was back to normal after 48h.