Mistake 1: Calling مُسْلِمَاتٍ in رَأَيْتُ مُسْلِمَاتٍ genitive just because it has kasra.
Correction: It is an accusative direct object, and this noun class uses kasra in the accusative.
Mistake 2: Reading مُسْلِمَاتٌ as accusative.
Correction: The ḍamma marks the nominative here.
Mistake 3: Giving every plural the same accusative vowel.
Correction: The ordinary fully declinable broken plural رِجَالًا takes fatḥa, while the sound feminine plural مُسْلِمَاتٍ takes kasra.