This looks like "white worm" corrosion, also known as filiform corrosion, which is a common issue with alloy wheels that occurs when the clear coat is compromised, allowing moisture and contaminants to penetrate and corrode the metal underneath.
Based on the images you shared, since all 4 alloys have developed this issue, it's apparently a factory defect where the protective coating is too thin or uneven, making the wheels vulnerable, rather than environmental damage.
You should escalate the claim to Kia Pakistan’s corporate office with supporting images and request a re-evaluation. Also google "white worm corrosion" to research this problem, that appears to be a common issue in diamond cut rims. The dealer's ignorance of this problem should not affect the company’s warranty liabilities.
As the damage is still in its early stages, the best course of action is to strip the old clear coat, clean the corrosion and apply a fresh clear coat, rather than replacing the rims.
