The trophy kit is made for racing, they probably didn't use bolts that were stainless steel or coated to resist corrosion as most race teams would care less if it didn't look good cosmetically. I understand that Stoptech sells a street version as well but it uses the same race calipers. Maybe they need to make a true street Trophy kit instead of an adapted race version...
I haven't seen this issue with the regular Stoptech street brake kits. Either way, it'd be interesting to see their response.