From: Rabbi Moshe Sofer
To: Rabbi Lipman
The Chasam Sofer rules that bloodstains found during the first three of the seven clean days cannot be attributed to the golden vein (orek zahav) condition, as the woman is considered muchzekes b'ro'ah during this period. As a practical remedy, he recommends performing a hefsek taharah after only two days of bleeding, which prevents the establishment of a confirmed-seer presumption and allows subsequent stains, after the required five days, to be attributed to the condition.
Source: Shu"t Chasam Sofer YD §165