Wheels washed with P21S Gel and thoroughly rinsed came out with stain blotches on the uncoated aluminum disk brake hubs. Is this a common thing? What went wrong?

P21S Wheel Cleaner Gel stains?-img_5118-jpg

I am working with the company to understand what the issue is, as it may not have anything to do with the product. Still interested in feedback from others who have used it and its interaction with uncoated aluminum parts.