We are currently fostering a female kitten age about 6mo. Before we have only had male kittens. This current one smells so bad! We scoop the litter tray 3 or 4 times a day and completely change and clean it twice a week. Open windows to air daily and clean and hoover her room. She is not allowed outside as she is a foster. Does anyone have any suggestions as to why she smells so bad and how we can combat it?