Is my action correct after I saw a brownish discharge and a spot of blood after performing ghusl during my usual menstruation days, and then I saw a transparent spot, tending towards pink and yellow, after the final ghusl, knowing that my period is 6 days and I do not see the white discharge (al-Qassah al-Bayda’)? And do I have to make up for (prayers) or offer expiation?

What the questioner did is correct. The brownish discharge (kudra) during the period of menstruation is considered menses, and the returning blood on the seventh day is menses because it is within the possible time frame for menstruation. What she saw recently is not menses. Purity is ascertained by inserting a cotton swab into what becomes visible when a woman squats for her needs, without exaggeration. She must abandon and struggle against her obsessive thoughts (waswas).