Rusting brake calipers

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Hello everone.
New 2009 X5 3.0 owner here. Purchased the truck with 59K miles about two weeks ago for my wife and she loves it!
I've owned BMW's since the 1980's including 320i, 318i 525i 545i 325i and 2 M3's and very familiar with the brand. One of the concerns that I have with the X5 is the rust/corrosion/pitting on all the calipers and rotor hats. It is a brown thick rust usually associated with rusting iron. I have never seen this on a BMW before. Usually it's a light grey type corrosion typical of aluminum.
The brakes work fine with the usual dusting on the front wheels indicating OE type pads.
The dealer and independant PPI said the rust is normal. The truck has been in N. Florida all it's live so as far as I know hasn't been exposed to excessive road salt.
Has anyone experienced this with the X5?
I plan to wire brush the calipers and rotor hats and paint soon.
Also, any recommendations on good caliper paint? I prefer to spray paint.

Thx in advance.