When there is a vowel /i/ in the last two syllables of a disyllabic or trisyllabic noun, and the possessive suffixes of the second and third persons are added, the final /i/ becomes lowered and centralized.
If a noun has an /i/ sound at the end of its two or three syllables, and you add the possessive endings for the second and third person, the final /i/ will move down in pitch and shift towards the center of the vowel sound.