Both the minor and major problems are related to each other. Yellowness is due to plaque in the teeth, which causes gum disease and leads to bleeding on Brushing. So get the Yellowish thing removed from a dentist by proper ultrasonic cleaning and polishing and the bleeding will itself stop in sometime.
Health Tips
Warm salt water rinses thrice a day till you get the procedure done
Omnident toothpaste to reduce bleeding on Brushing