TT #181 · Parshas Tazria · Aliyah 5 · Passuk 27
English: The priest shall examine him on the seventh day. If the lesion has spread in the skin, the priest shall pronounce him unclean; it is a tzaraas affliction.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:27
Torah Temimah cites Sifra (Toras Kohanim) for excluding spread into a bright spot at the end of the week after release.
Sifra — Vayikra 13, Midrash Sefer
English: 'It is' excludes spreading into a bahak at the end of the week after release.
Textual derivation
This exclusion is specific: spreading into a bright spot at the end of the week after release does not count under this rule.