The band began to spoil

Hi

Apple advises that band colours may vary or fade over time.

To help avoid stains or other damage, be sure to always handle your Apple Watch and the band in accordance with Apple's cleaning and care instructions. They include cleaning and drying your watch if it comes in contact with anything other than fresh water:

• Cleaning your Apple Watch - Apple Support
• Important handling information
• Band care information

Apple Watch bands are covered under Apple's Limited Warranty against defects in materials and workmanship, but not against normal wear and tear or misuse.

If you are concerned that your band is defective, then contact Apple Support (mail-in service may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider to arrange for it to be inspected and, if eligible, replaced under warranty:

• US: Apple Watch Service Answer Center - Apple Support
• Elsewhere: Select your country for Apple Watch service and repair information

I really can't tell anything from the picture you posted. Make a Genius Bar appointment at your nearest Apple Store and have someone from Apple look at it.