Hello, iron supplement stains are common
Since scaling only provides a temporary fix for you, we need to look at why the stains return so quickly.
Next Steps
I recommend a professional Air Polishing session (using a prophy jet), which is often more effective for deep extrinsic stains than regular scaling. If the stains are very deep, composite veneering or bonding on the front surface can provide a long-term aesthetic solution.
Health Tips
Try drinking your iron supplements with a straw to avoid direct contact with front teeth, and rinse your mouth immediately after every use.