Its possible that its the wax from the car wash that caused the discoloration on the rims. I wouldn't say they were damaged. haven't any of you guys accidentally put wax on your flat black plastic trim pieces? It will cause a "discoloration" but its really the wax. I believe this is the same issue. Matt black or flat black paint is not perfectly smooth, its almost porous like in that any dirt or wax will build up in the grain of the paint. On plastic the only method is to use armor all. For rims theres similar detailing products that you can use on your rims.
use dish washing soap and hot water and a brush and wash those rims one more time to see if they come clean. You may have to use some elbow grease. If not then hell, shoot 'em down with some armor all and wipe them down... Good as new...