It was dragons blood iron remover, it's ment to be ph neutral, but in my defence was left no longer than the other 3 wheels that didn't show up with the same contamination, My process is jet wash the wheel, spray on iron cleaner, scrub with detailer bush, wash with oh neutral soap and water then jet wash off again. I do each wheel individually and I've never had this issue before and I've been doing it that way for 20 years.The staining looks to me like wheel cleaner that has been left to dwell for too long.
After one initial deep clean, I've never had the need for cleaners. Shampoo and a wash mitt cleans them easily enough.
The only time I've ever seen anything like this is a reaction from wheel acid which I never use.