Grey Baby Parrot sound

by Shabbir
(Kuwait)

We got a Baby African grey parrot a week before the time we purchase from a local bird market here in Kuwait his sound was clear and loud saying koko koko but from next day in our house we feel his voice is bit low like a very small chic or like when something stuck in his throat but some time it's clear.

His eyes are full black and on his leg ring is written (57. 11 EJG) we don't know the his age but as per seller he is 5 month old. We feed him sunflower seed, almond, nuts, apple and pomegranate . He eats and fly normally looks healthy except this voice. Is this normal for a baby parrot ?