arpan2308 instead of buying a new one, just get your Spigen case replaced by the brand. Both Spigen and Ringke come with warranty, and yellowing is covered under that. I’m confident because I’ve had personal experience with ringke, I wrote them an email with pictures and invoice attached, and within a week they sent me a new one.
If you bought it via amazon, then they can also help you out with replacement or refund. The second time I had issues with the case Amazon India issued me a full refund.
That’s the only benefit of buying an expensive case.
See every transparent case gets yellow, some within days others within months. It is what it is.