The more airflow that passes over a wing the more lift it creates (By creating a low pressure area above the wing), the less the airflow the less the lift. Imagine your doing 160kts IAS on approach (this includes any headwind, in this case 50Kts). If you suddenly lose 35kts of this headwind then you have lost 35kts of airflow over the wing. Remember less airflow = less lift, and you will go below the G/s.