Fading and discolored bottles

The bottle markings are fading and the name on the front both my kids are using the bottles and have to keep buying new ones after sterilizing them and using it for 2-3 months the bottles have a discouloration and a smell using ur sterilization and brush

The product boast to be the best on the market but can’t help a mum put trust in a product as it doesn’t last yet is so expansive