To clean your Beoplay H9i, you should only use a soft, damp cloth.
Leather is a natural material and is therefore subject to change over time and with daily use. Irregularities in the consistency and depth of the colour should not be considered a fault but inherent to the natural beauty of the leather.
Changes in the colour of the leather and signs of wear are normal. While occasional exposure to water is not a problem, leather is not waterproof, and a periodic treatment with neutral coloured leather grease can improve appearance and longevity.