Hi gum bleeding can be because of dirt/calculus as well as food lodged in cavities between two teeth. reappearance of stains after scaling can be due to lack of proper oral hygiene maintainance.
Smoking or intake of colored beverages can bring about the reappearance of these yellow stains faster.
Next Steps
visit a dentist and get a check up done
Health Tips
always make sure that a thorough polishing is done after scaling because after scaling there is always microscopic roughness on the tooth enamel which has a high surface energy to attract dirt and Debris back onto the tooth surface. once polishing is done the enamel becomes smooth and Debris won't easily settle on the enamel. but always remember all this won't apply if you fail to establish good oral hygiene regime post scaling.