Ok, it appears to be mineral deposits. Nothing more than calcium and other minerals found in water. Once the water evaporates the minerals are left behind leaving their unsightly stains. If you have any glazes around like 3M hand glaze I would try this in a small spot. Any automotive glaze would probably work. If you don't want to go with the glaze you can also try the vinegar wash. Mix about 1 part vinegar 3 parts water and try in a small spot. Work the solution in with a soft microfiber and rinse. You can go as strong as 1:1 vinegar:water, but start light and always spot check. Once you remove the spots I would sugest you put a good wheel sealant on your rim like Wheelwax or RimWax. This will make subsequent cleaning much easier. I hope this helps. If you have any other questions don't hesitate to ask.
Brett @ OCD