Interestingly the Sunncamp uses a 150 D Polyester material pretty much the same as the Kampa range.
For those of you into Stockings you will know the D stands for Denier , the weight of the yarn used to make the fabric.

You will see from previous threads my own Kampa Rally Air Pro survived two major storms last year. The leg failed but the fabric remained intact.
The Isabella on the other hand has a material twice the rating of the Sunncamp and Kampa. But it comes with a price tag of £1200+.
To say air ones are rubbish would be very unfair but as an earlier poster said . You pays your money and .....
The discolouration is worrying. Most disappointing the Sunncamp team haven't answered you. What warranty did you receive at time of purchase?